Networking on Facebook is called as social networking.
Social networking is the practice of expanding the number of one's business and/or social contacts by making connections through individuals. While social networking has gone on almost as long as societies themselves have existed, the unparalleled potential of the Internet to promote such connections is only now being fully recognized and exploited, through Web-based groups established for that purpose.
Based on the six degrees of separation concept (the idea that any two people on the planet could make contact through a chain of no more than five intermediaries), social networking establishes interconnected Internet communities (sometimes known as personal networks) that help people make contacts that would be good for them to know, but that they would be unlikely to have met otherwise. In general, here's how it works: you join one of the sites and invite people you know to join as well. Those people invite their contacts to join, who in turn invite their contacts to join, and the process repeats for each person. In theory, any individual can make contact through anyone they have a connection to, to any of the people that person has a connection to, and so on.