Here's a break down for the most part...
+o (@) - Operator
Ban, Kick, Voice, Channel Modes, etc. Basically everything but /chanserv <commands>
+h (%) - Half Op [Helper]
The majority of the following but, depending ont he server, some disallow banning, where tohers disallow kicking also. You also can not give clients operator when you are a Half-Op.
+v (+) - Voice
This is masically to bypass the +m (moderated) channel mode. Some channels use +m so that people cannot talk unless given the permission to. The permission is assigned my either +v, +h, or +o. If you do not have any of those modes, a client cannot talk in the channel.
Thats a sum up of the modes. As I said, all servers are different, but thats *usually* how it goes >:D