Why do they call it a pump track?
BMX pump tracks are named as such because they are centred around the rider using a pumping motion to generate and maintain speed around the facility, avoiding the need for pedalling. This basically means the rider assumes a crouched position, extending vertically as you ascend a rise (i.e. a roller or corner) and then compressing (or pumping) as the descent of the rise occurs. This motion pushes energy through your bike and into the ground, propelling the bike and rider forward.