(In social media and the internet)
Follow is a subset of Friend.
When you add someone as a Friend, you automatically follow that person, and they automatically follow you (under the assumption the friend request was accepted).
Most social websites, offer a service titled Follow. This means exactly what it says—you will subscribe to updates from that person you follow.
The buzzwords used here denote the type of relationship you can or have established with another person in the digital world. Their origins: Real Life.
Other paradigms I've heard of...
Groups—Collectively refer to a group of friends or followers.
Connection—This is used by LinkedIn to connect you to people you might know, have worked with etc.
Guild or Clan—Popularly used in video games to collectively refer to a group of people. Also see. Guild Member, Clan Member, Guild Leader, Clan Leader.
Community—Collection of Friends, Groups, Connections, Guilds/Clans sharing or having certain attitudes and interests in common. Also see. Community Member, Community Moderator, Community Administrator.