How Facebook Works?

In 2004, Mark Zuckerberg, Dustin Moskovitz and Chris Hughes, three Harvard University students, launched a Web site designed to put students in touch with one another, share their photos and meet new people. They called it thefacebook.com, and before long the site became extremely popular on the Harvard campus. A month after the site launched, the creators expanded it to include students from Stanford, Columbia and Yale. By 2005, students in 800 college networks across the United States could join the network, and its membership grew to more than 5 million active users. In August of that year, the site's name changed to Facebook.


Facebook was originally intended for college students, but today anyone can join the network. Although the site's scope has expanded to include more than just students, its purpose remains the same -- giving people a way to share information in an easy and entertaining way. Like MySpace, Facebook is a social networking site.

To explore Facebook, you must create a free account on the site. Facebook's terms of use state that members must be at least 13 years old, and any member between the ages of 13 and 18 must be enrolled in school. Facebook requires new members to provide a valid e-mail address before completing registration. Once you've created an account and answered a few questions about where you work, where you went to school and where you live, Facebook will generate a profile for you.
­­Facebook provides several ways to find friends:

• You can browse and join networks, which are organized into four categories: regions (networks that are linked to specific cities or countries), colleges, workplaces and high schools. Once you join a network, you can browse through the list of members and search for people you know. You can sort people by age, sex, relationship status, political views and other criteria.
• You can let Facebook pull contacts from a Web-based e-mail account. To do this, you have to give Facebook your e-mail address and password. Facebook uses a program that searches through your e-mail contacts and compares the list against its membership database. Whenever Facebook discovers a match, it gives you the option to add that person as a friend.
• You can use Facebook's search engine to look for a specific person. Type the person's name into the search field, and Facebook will display any profiles that match the name.

Facebook Profiles
Your Facebook profile is the Web page other members will see if they look you up. It gives people an idea about who you are and what your interests include. Facebook assumes that many of the people with whom you'll want to connect work for the same company, went to the same school or live in the same town as you.
To make it easier to find friends both old and new, Facebook gathers information about you and everyone else to create a dense network of contacts. The upside is that you'll be able to see old classmates or coworkers who have Facebook accounts; the downside is that everyone else in that network will be able to find you. You can choose not to answer questions or to adjust privacy settings so that others can't find you, but that tends to defeat the purpose of a social networking site. ­
Your unmodified profile has:

• A space where you can upload a profile picture.
• A friends section, which displays pictures of Facebook members you've befriended.
• A section that shows the personal information you've decided to share with other members. This can include your birthday, work history, education and interests.
• A mini-feed section, which informs visitors about what you've been up to. If you change your profile picture or add a friend, the mini-feed will display a message about it.
• A comments section called the wall, where other members can leave messages for you.

 If you visited another member's unmodified profile, you'd see the same fields and sections, but under his or her profile picture you'd have a few more options, including:

• Instant message, which opens up a Facebook application IM client
• Sending the person a message, a function similar to e-mail
• An option to add the person as a friend, if he or she is not already your friend -- the next time the other member logs into Facebook, he or she will see the friend request and can accept, reject or ignore it.

When you log into your account, you arrive at your personal Facebook homepage. The basic homepage layout includes a news feed that keeps you updated about what your friends and networks are up to. There's also a status update section, which contains notices about messages you've received, invitations to events, notices about applications your friends would like you to try and a place where you can tell people how you're feeling or what you're up to. There's also a link that lets you invite friends to join Facebook.

Dynamic Profiles

Facebook designed profiles using dynamic hypertext markup language (DHTML). This means that you can change the layout of your profile simply by clicking on sections, such as your information box, and dragging them to another part of your profile.

 Business owners, artists, bands and public figures can make special Facebook profiles. Instead of becoming friends with the owners of these accounts, you can become a fan. If you work for a company that doesn't have a presence of Facebook, it's a good idea to discuss a strategy with others before creating an account -- most human resources departments don't care for surprises.

You can customize your Facebook profile using Facebook applications, some of which were developed by members just like yourself.

Facebook Applications
Facebook's applications set it apart from other social networking sites. Facebook's first-party applications include photos, videos, groups, events, marketplace, posted items, notes and gifts. These are applications developed by Facebook and available to all members. Here's a quick breakdown on what each application does:

• The photos application allows you to upload as many images as you like. If you have a picture of another Facebook member, you can tag the photo with that member's name. After tagging the photo, it'll appear both in your photo album and on your friend's profile.
• Facebook's video application is similar in many ways to YouTube. Members can upload videos in almost every format, but Facebook requests that all files remain below 100 megabytes and that videos be shorter than two minutes. Facebook converts videos into the flash (.flv) format.
• With the groups application, you can join other members' interest groups or you can create one of your own.
• The events application allows you to invite other Facebook members to a real-life gathering.
• Facebook's marketplace is a lot like craigslist -- it lets members connect with other people who want to buy or sell stuff. All transactions occur directly between members -- Facebook only hosts the exchange; it doesn't get involved in sales.
• The posted items application can be used to post videos, songs or anything else on a Web page to your profile. All you have to do is enter the Web page's URL into the post field on Facebook. The application generates a thumbnail of the target page that acts as a hyperlink. Your friends can click on the thumbnail to visit Web sites that you think are cool and interesting.
• With the gifts application, you can send another member a virtual gift in the form of a small icon. There are dozens of gifts to choose from, all designed by Susan Kare, who created the icons for the original Macintosh computer system. The first gift is free, but all subsequent gifts cost $1 and require a credit card -- Facebook doesn't accept PayPal. Facebook donates proceeds from gift giving to charitable organizations. Gifts can be private or public, and you can include a message with your gift.

 Facebook is always working on developing new applications for members. If you're familiar with Facebook, you know there are hundreds of other applications available on the site. Facebook didn't develop these applications -- other Facebook members did.
Many sites give users limited access to an application programming interface (API), which lets users develop applications using the host site as a platform. But for most of these sites, user applications aren't featured on the site prominently. Third-party Facebook applications can dramatically change your experience on the site, including a massive overhaul to your profile page. Your simple profile can transform into an exciting page that includes videos, product reviews, games and virtual pets. But there's also the potential for chaos -- if you activate too many applications on your profile, it will become a sprawling Web page that other members might find difficult to navigate.

Third-Party Facebook Applications
To create applications in Facebook, you first must add the Facebook developer application to your profile. You also must have access to a Web server where you can store your application -- Facebook does not host third-party programs. Applications can be Web-based, desktop-based or mobile-device-based. In other words, you can create applications that take advantage of the Facebook platform but aren't incorporated into member profiles. For example, it's possible to program an application that creates a window on your desktop that is linked to your profile's news feed.

 Facebook says that its application programming interface (API) is based on a Representational State Transfer (REST) interface, a term coined by Roy Fielding in his Ph.D. dissertation at the University of California, Irvine. In a REST network, form follows function. Fielding's ultimate REST network was an idealized version of the World Wide Web that had independent components that worked together to maximize the efficiency of data transfers [Source: Fielding].
In terms of Facebook's API, a REST-interface means that applications interfacing with Facebook send method calls using Hypertext Transfer Protocol (HTTP) GET or POST requests. HTTP is the communications protocol used by the World Wide Web -- the GET request retrieves information and the POST request adds information to an existing Web page. This means that Facebook applications can retrieve information from member profiles, post messages to profiles or do both.
Developers can also use the Facebook Query Language (FQL), which is similar to Structured Query Language (SQL). Query languages are programming languages designed to retrieve information from databases. With FQL, a developer can obtain information about any user who downloads his or her application. In a way, that's really what Facebook applications are all about -- gathering information about users. Developers could use this information as a way to create target audiences for advertising or build a consumer base for a particular product. Facebook has been criticized by people who believe the site allows application developers to gather data from members, including personal information and Web surfing habits.

For those developers who want to create applications that deeply integrate themselves into Facebook's platform, there's the Facebook Markup Language (FBML). Facebook derived the language from HTML and added some site-specific tags. Using this language, developers can create applications that become a more integral part of the user's Facebook experience, affecting profile appearance and function.

Every application has a space on Facebook called a canvas page, which developers can use however they wish. When a user clicks on an application icon, his or her web browser goes to that application's canvas page. Developers can include Web advertising on canvas pages, sell products using a Facebook-designed interface or simply share information with the user.

Facebook Facts and Figures
While the company began as the pet project for a group of Harvard students, today it calls Palo Alto, Calif., home (the company also has an office in New York). Facebook has more than 350 employees, and the benefits package sounds pretty sweet. It includes:

• Medical, dental and vision health plans with no premiums
• 401(k) plan
• Four weeks vacation and eight company holidays
• Free catered breakfast, lunch and dinner every day
• Dry cleaning and laundry services
• An IBM Thinkpad or Apple MacBook Pro -- employee's choice

Facebook's popularity continues to grow day by day. The company claims that it has more than 57 million active members -- users who have logged onto Facebook over the last 30 day period -- on the site. Since January 2007, the average number of new registrations per day is 250,000. Facebook says that the number of active users doubles every six months. Members from the United States account for most of Facebook's population, followed by members in Canada and the United Kingdom.
Facebook also claims to be the No. 1 image-sharing service on the Internet, drawing more traffic than the second-, third- and fourth- place sites combined. In terms of image numbers, this means that Facebook receives more than 14 million uploaded images every day. Because there's no limit on how many images a member can upload and new members arrive at Facebook every day, this number will likely continue to rise exponentially.
Since June 2007, when Facebook first allowed third-party developers to create applications, developers have debuted more than 7,000 programs on the Facebook platform. Every day, developers introduce another 100 applications to the site. Facebook estimates that more than 80 percent of all members have used at least one third-party application.

Mark Zuckerburg, founder of Facebook, explains the concept of Facebook's social network. The site has grown from Zuckerburg's vision of connecting the Harvard campus to connecting users across the Internet. 

Because it is so popular and heavily trafficked, Facebook requires massive amounts of storage space, both in a digital and physical sense. According to one Facebook employee, the company relies on around 200 memcached servers for production (day-to-day operation of the site) and a few more for developmental purposes [source: Grimm]. "Memcached" stands for memory caching, a method of temporarily storing data. A memcached server temporarily stores information in the server's memory, reducing the need to search a database for information. This decreases the amount of time it takes between a request for information and the delivery of that data.
Facebook also uses custom-built servers for back-end operations and a monitoring system to keep track of all the servers. Servers take up space, so Facebook leases facilities from vendors for server storage. In 2007, Facebook signed an agreement with DuPont Fabros Technology (DFT) to lease 10,000 square feet of space in an Ashburn, Va., storage center [source: Data Center Knowledge].
So how does Facebook make enough money to cover its expenses? It generates some revenue by selling web advertising space, but the majority of its funding comes from private investors. According to Facebook, it has received more than $40 million in funding since it launched in 2004.

Source :  HowStuffWorks - Facebook