Permissions Groups

Can someone explain how to use Permission Groups to me?

In particular, I can't seem to figure out how to assign players to a group.

Administrative control panel->Groups

Yes, I know where the controls are. I'm just not sure how to use them. How do I assign players to a group? Is that field expecting a comma-separated list of player names?

I don't think it works at the moment. I don't believe it was completely implemented

Cancerman explained it here...

That’s what I ended up doing, but I spent a while trying to figure out how the groups thing works and having no luck. This works, I just was trying to leverage the groups thing rather than set each people individually.