facebook, myspace, twitter etc. if you have something to sell, you can try selling it to people on those networks. However, as they go on there to socialise, not be spammed to death, you need a light touch, the ability to communicate, and the use of humour and tact to not be reviled and banned.
Social Networking sites are basically ways of getting connected with your friends. Things like myspace and facebook. Mainly, they don't make you money directly, but they're used for advertising. This works by building a profile, making loads of friends (who would be interested in your product/website) and then occasionally sending them mails. If you do it too much, then people will stop being your friend and you risk getting your account banned.
A social network is a social structure which, in general, facilitates communication between a group of individuals or organizations, that are related by one or more specific types of interdependency, such as: a special or common interest; shared values; visions, ideas, or perhaps ideals; financial exchange, friendship, kinship, dislike, conflict or trade.
I was about to search the meaning of social network... well anyway, those social network sites are friendster, facebook, myspace etc.