Minecraft wiki entry for Custom_maps, associated text: Race For Wool maps. This is when teams of four go into a lane and try to complete a monument there. They include dungeons and crossfire from the other lanes. This is a type of CTM.
Capture The Wool maps. This is where people rush to the opponent's base and attempt to steal wool from a fleecy box (wool chest). They then have to return to their base. Can be played in small or large groups.
Destroy the Monument/Core maps. Self-explanatory. Usually only played in large groups, sometimes up to 50v50.