By drawing the combo tag, you get a general deer and elk tag. About 50% of the state is good on the general elk tag. You can hunt any of the general units with a general tag, they're not unit specific.
After you have the general tag, you can apply for a special permit, which allows you to hunt in a specific unit that requires a permit.
You'll have to read up on the regulations on what each specific unit is. For the most part though, the west side is general units, and the east side is special permit only.
For deer, almost all the state is open for whitetail on the general tag, and maybe 3/4 is open for mule deer. Same thing as elk, you can apply for a special permit after you draw your general tag. If you draw a mule deer permit, you are only allowed to hunt mule deer in that unit, but you can still hunt whitetail in any general unit.