A social network site concentrates on constructing online communities of persons who disclose and share interests, hobbies and activities and who are also interested in discovering the same about the others on the net. Most of the social networking sites offer an assortment of methods of user interaction such as e mail and instant messaging and are web based.

Social networking now has in fact become an entirely a medium of social interaction, communication and information sharing on the virtual world. Today, they have an extensive usage and have attracted millions of users. For several years now, they have become the cream of the new online media. Their unique feature has been the ability to attract millions on new individual users.

In fact, the traffic generated by the social networking sites is second only to those generated by the search engines. These sites have also opened an excellent channel for businessmen for advertising his product or service.

Currently there are many popular social networking sites online. Some of them are:

• My Space: used globally, a general site for communities
• Face book:  also used worldwide, for general communities
• Orkut: general community site, popular in South and Central America
• Bebo:  a community site based in the U.K
• Twitter: A microblogging site most widely in North America
• Flick: a picture and photo sharing site
• You tube : a site for video networking
• Linked in :  A popular site mostly being used in North America for professional business networking

Presently, the social networking sites are worth billions of dollars as an advertising medium.