What is Warden?
Warden is a software running on Blizzard’s warcraft servers. It scans your files/memory for forbidden modifications of the gamefiles such as hacks. If it detects a cheat, it will ban you. You can protect yourself with tools like DropBnet.

What are cheated maps?
Cheated maps are modified original maps. They have new triggers that activate cheats, e.g. gold-, exp- or manacheats. In contrast to collided maps every player has to have/download this cheated map to play together.

What are collided maps?
Collided maps a slightly modified version of the original map in order to give you a few visual advantages. If you use a collided map, you can still join games which run the original map! So only you get those advantages.