I added the Power Control widget to my home screen. While I am pretty certain about 4 of the 5 switches - wi-fi, bluetooth, gps, and screen brightness, I don't know what the 5th icon is for. The round one with the clockwise arrows. BTW, this standard Android widget looks a lot better, especially on a black background, than the ugly Moto toggles.
It's the "Refresh/auto-sync" button. It controls your PUSH email (ie. GMail, Contacts, Calendar) from automatically syncing without requiring u to go into the app and click Menu > Refresh
