The parking brake (sometimes erroneously referred to as the "emergency brake") acts only on the rear wheels of modern cars--including those that are front-wheel drive, rear-wheel drive, and 4 wheel drive. There may have been some cars in the distant past whose parking brake worked on the front wheels, but those days are long gone.
However, if you are actually referring to the "park" function of the transmission, that is a different story. On a FWD car, engaging the park position of the transmission causes the front wheels to be locked in place. Similarly, on a RWD car, "park" locks the rear wheels. And, on a vehicle with permanent AWD, "park" position on the transmission locks all 4 wheels.
Essentially, the drive wheels are the ones that are acted upon by the park function of the transmission, and the rear wheels are the ones acted upon by the parking brake. Which of these are you actually referring to?