Tags are an in-game feature that allow for the identification of someone's role in game. Currently, there are six tags, each assigned for different reasons. First, the developer tag, as it name says, identifies a developer.
Admin EditThis tag identifies an administrator.
This tag identifies someone who is testing beta features of the game.
All of the levels (Bronze, Silver, and Gold) identify someone who has donated. The level seems to depend depending on the amount that has been donated.