The social nets exist very before the Internet. One is about a sociological phenomenon that congregates the union of groups for the common constitution of relationships and other ends (this is the reason of some to classify sites as the Orkut, for example, as site of relationship). The question is that with the advent and the power of abrangncia of the Internet these nets had approached people who before depended on a physical social bond as clubs, churches, events in general, for the congregation of objectives. It is important also to differentiate social nets, sites of social nets and communities. The sites of social nets congregate through the Internet the social linkings that a person possesss as friends, fellow workers, among others actors who not necessarily are known of the user in the physical world, but will go to have some contact with the user through the Internet. While, through the communities the people will go to argue on definitive subjects as: Professionals: where specialists in determined pursuings debate on its professional field; Leisure: where people speak on common interests as teamses, hobby, games, etc; Support: meeting of related subjects the illnesses, difficulties, vices, etc. also Has those communities where the users look for information on definitive products, services or same to complain. Being thus, the Internet consists as an important tool for the social nets and the approach on that before they depended on physical events (it are of ciberespao) for constitution of its communities..