Welcome to GameToast
Well to start off, Maps and mods are different in a few ways, but making them uses the same munge process
-A mod doesnt have to have any maps in it, it can use the stock maps.
-A mod 99% of the time changes the sides ie The republic clones might have new skins amd new abilities.
-Mods are tougher and simpler to make than maps.
I suggest you check out
TheEverythingYouNeedToKnowThread and read as much as you need. READ ALOT
-you need to know the basics of side editing
-you need to know the basics of lua editing ( Lua is the game script, most of the basic stuff is simple, but when you get into advanced modding, you can do all sorts off cool stuff, like campiangh modes