facebook's definiton

There are many kinds of social networking service in the world wide web that allow users to interact and share data, and the most popular one is facebook. Because of its popularity, there are more than 600 million active users of facebook around the world. Facebook can also be called as a digital book which is used by people to see somebody or deal with something by interacting each others in website, in a world where the people can interact one another although they do not face to face.
The registered users of facebook may create their personal profile with uploading photos and video, lists of personal interests, contact information, and other personal information. They also can keep in touch with friends, family, colleagues, and other users through public or private messages and a chat feature.
Facebook has a number of features which the users can use. Including the Wall, a space on every user's profile page like a virtual buletin board where friends may post messages for the user to see. The messages left on members’ wall can be text, video, or photos. The second is Poke, it is one of the features that allows users to poke each other virtually. There is also Photos Aplication. By this feature, the users can upload their an unlimited number of photos and make albums from the desktop or directly uploaded from cell phone camera. Beside that, they can tag or label users in a photo. Another one is Status Updates, a microblogging feature used by the users to inform their friends of their whereabouts and actions. The next feature which is introduced is Facebook notes, it is a blogging feature that users can share their short written records which can be embedded with images and tag their friends there.
There are also others public features such Marketplace where users can post, read and respond to classified advertisements. Faceebook also set Groups that allows the users who have common interests to find and interact each other. If the users have some events, they can publish them in facebook and invite guests to attend. Beside those, the Pages Feature is also had to allow members to create and promote a public page built around a specific topic. The users can also have an instant messaging application called chat to communicate with friends.
All those interactions are published in a newsfeed in homepage, which are distributed in real-time to the members’ friends and can be read by others. However, the information and updates which are shared in the newsfeed depend on the users’ privacy. Facebook has given right to users in order them to be able to  control what types of information shared automatically with friends. Beside, they can also set categories of friends who are able to see updates about certain types of activities, including profile changes, Wall posts, newly added friends, notes, pictures, status updates, and others.