A social network describes relationships between users and allows other functionality to use those relationships as inputs and filters. Common social network features include:
- allow users to mark each other as a connection of one or more kinds (e.g. Contact, Friend, Circles, etc)
- block users from some or all content or access or interaction
- form and join and leave groups
- interact with neighbors and others nearby on the resulting graph
Contrast to a flat forum where all users can see and interact with each other equally.