Categories of social network.

A social networking web site, also called an online social network, is a web site that encourages members in its online community to share their interests, idea, stories, photo, music, and videos with other registered users. Most include chat rooms, newsgroups, and other communication services. Some social networking web site are college oriented, some business oriented, and others are more focused. Popular social networking web site include Myspace and Facebook, with Facebook alone boasting more than 300 million active users.

A media sharing web site is a specific type of online social network that enables members to share media such as photos, music, and videos. A photo sharing community, for example, is a specific type of social networking web site that allows users to create an online photo album and store and share their digital photos. Flickr, Fotki, and Webshots are popular photo sharing community. Similarly, a video sharing community is a type of social networking web site that allows users to store and share their personal videos. PixelFish and Youtube are popular video sharing communities.

A blog, short for Weblog, is an informal web site consisting of time-stamped articles, or posts, in a diary or journal format, usually listed in reverse chronological order. Blogs reflect the interests, opinions, and personalities of the author, called the blogger or vlogger (for vlog), and sometimes site visitors. A blog that contains video clips is called a video blog, or vlog. A microblog allows users to publish short messages, usually between 100 and 200 characters, for others to read. Twitter is a popular microblog. The term blogosphere refers to the worldwide collection of blogs and the vlogosphere refers to all vlogs worldwide.

A Forum, also called a message board, discussion group or bulletin board, is an online discussion site where people can hold conservations in the form of posted messages. Depending on the forum set-up, users can be anonymous or have to register with the forum and them subsequently log in in order to post messages. Also, depending on the access level of a users, a posted message might need to be approved by a moderator before it becomes visible. A forum is hierarchical or tree-like in structure : forum – subforum – topic – thread – reply. An internet forum can be focused on nearly any subject and a sense of an online community, or vitual community, tends to develop among forum members.