For movement on the ground the aircraft uses it own engines, however since the aircraft cannot move backwards on its own, there are pushback trucks on the airport
A pushback truck lifts the front weel of the aircraft, their role in most airports is to move the aircraft away from the parking spot on to the taxiways. Here the truck is removed and when all platform staff is out of the way the engines are started one by one. From here on the aircraft moves on its own power to the runway. In the aircraft you will hear the engine spinning up when power is demanded for acceleration.