The acronym PRNDL stands for park, reverse, neutral, drive and low. These letters are typically located on the gear shift of a car, on the dashboard or on the steering column behind the wheel.
Park, reverse, neutral, drive and low are the various states that a car can be in. When the car is parked it isn't moving, and when it is in reverse it goes backwards. When it is in neutral the gears are not engaged, and drive means you are going forward. Low shifts to a lower gear for difficult road conditions like hills that require more power rather than more speed when you hit the accelerator.