Wheel offset is moving the mounting hub (wheel spoke) away from the center line, either positive (moving it toward the outside, or fender side) or negative (moving it back or toward the brake disk) A deep dish is a large amount of negative spoke offset... the further back the mounting hub (wheel spokes) goes in the wheel, the more offset or deeper the dish becomes. Deep offset has nothing to do with wheel width so you will be able to use your regular tires.

You can get wheels with a lot of offset at www.r2hobbies.com