SNS is a mature and popular information carrier, such as short message service. Another common explanation of SNS: the full name of social networking site, namely "social networking site" or "social network". Social networking site refers to the relationship network between individuals, and this kind of website based on the idea of social networking relationship system is social networking site (SNS website). SNS also refers to social network software, which is the next generation of personal-based network basic software built by using distributed technology, which is popularly called P2P technology.
1967, Stanley milgram, a professor of psychology at Harvard University (1933 ~ 1984) founded the theory of six-degree division, which simply said: "There will be no more than six people between you and any stranger, that is, you can know any stranger through six people at most." According to the six-degree segmentation theory, each individual's social circle is constantly enlarged and eventually becomes a big network. This is the early understanding of social networking sites. Later, according to this theory, some people established Internet services for social networking sites, and expanded their social networks through "acquaintances of acquaintances", such as ArtComb, Friendster, Wallop, adoreme, etc.