When something is moving it has energy. Imagine trying to stop a run-away horse or a rugby forward moving at speed. This type of energy is called the KINETIC ENERGY of the object.
There will be more energy ‘locked away’ in a massive lorry that is moving at 20 m/s than in a motorbike travelling at the same speed and the faster it goes the more kinetic energy it has.
The kinetic energy of an object therefore depends on two things:
(a) the mass of the object (m)
(b) its speed (v)