Web resource (portal), within which each registered user receives a template personal page for posting data about himself, as well as content various species. A feature of social. networks is the ability to communicate their participants through messages and content sharing.
In most existing social. networks there is the possibility of creating thematic groups that are actively used in SEO to popularize web resources and form social signals, which are more and more readily taken into account by search engines when constructing an issue.
External reference profile, formed using links to the site from social networks, search engines consider the most natural.
In social networks there is the possibility of placement targeted advertising, which can also significantly increase the flow traffic to the website.
The most effective for promoting sites are social. network Facebook, Vkontakte, Google+, Twitter.