Answer:
The DVD game by Imagination Entertainment comes with 2 dance mats that Do Not hook up to a game system or the tv. If you get a game system like a Xbox (original or 360) or the playstation 1, 2 or 3 then you will have to get a dance pad or 2.
When buying my Dance Dance Revolution (DDR) game, I needed to buy my mats separately. I reckon one mat would have cost around US $40. I had a PS2 at the time, and could only fit 2 mats to a game. If there are more players, try out the 'Party Mode' where players rotate around the mats.