Adventure Map - The map where you do your exploration. It shows the castles, mines, resources, and other structures in the world.
Combat Map - The map battles are fought on. It is made up of hexes.
Hex - One six-sided space on the combat map. This is clearly illustrated by going into Combat Options and turning View Hex Grid on.
Retaliate, Retaliation - A counter-attack a stack of creatures performs after it is attacked.
Stack - A group of creatures shown on screen by a picture and a number. (ie a hero can have seven stacks of creatures in it's army)