It's part of the forum code. In some websites and forums the group function is used generally to represent moderator teams. In a very large forum where there are so many mods, it is easier to say that A group is covering these few boards and B group has those other ones.

On CSS Forum there aren't any public groups or usergroups yet.

It's possible for Admins to set up usergroups, which people can join and admins can then give someone moderator rights for that group, so that they can choose who joins, and set up forums that only that group can see.

An example would be the 'SPSC' sub-forum. Presently it is completely public, and there's no usergroup associated with it. However, a 'SPSC' usergroup can be set up and that sub-forum can be made visible only to the 'SPSC' usergroup.

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