How can an object at rest have energy?

An object at rest inly has potential energy, meaning if a ball sat on the ground, unmoving, it has potential energy and if you push it, that becames kinetic energy which is the energy of movement. And also remember that that higher an object is, the more potential energy it has, meaning if you have one ball sitting at the top of a hill and other ball sitting of flat ground and pushed them both with the same amount of force, which one would travel faster? The ball on the hill because it had more potential energy to start with since it was up high so when u pushed it, it moved faster than the ball on flat ground. You get it? I hope this helped.
you need to consider the different forms of energy an object can posses