Follow adds sitewide and per user links that link to various social networking sites. The links reside in two blocks. The Follow Site block lists all the links for the site itself, and by default is visible on all pages. The Follow User block lists all the follow links for the user and is visible only on user profile pages.
It is recommended to enable a module such as external that will pop open
the follow links in a new tab or window, as target="_blank" does not validate.
Here's a list of some of the currently supported social networks: