Alex, in addition to the link Hal provided there are a couple of other functions a moderator can perform that aren't mentioned there. First, is the ability to create announcements for your forum. Another relates to identifying an IP address if IP logging is turned on. Mods can also edit/prune their forum messages via the control panel. Those are a few I can think of.
To find out how, contact your board administrator so he/she can show you where you need to do these things on his/her site.
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Doug
darksaber.hispeed.comI am altering the deal. Pray I don't alter it any further.
--Darth Vader, The Empire Strikes Back