Illustration for gravitational potential energy

You could also imagine the work necessary to completely separate the two.

One of the key concepts to help understand binding energy is the concept of escape velocity in gravitational systems. An object's escape velocity is determined by the kinetic energy necessary for it to overcome gravitational binding energy.

Picture two objects, bound in a gravitational system. They have fallen together into a potential energy well. In our way of modeling it, complete separation is zero potential energy. All other values as negative.

Assume one object is the Earth and the other is a baseball. The escape velocity represents the speed the baseball would need (if there were no friction) to climb all the way out of the potential energy well it has fallen into with the Earth. How much kinetic energy would you need to add to make the total energy (potential plus kinetic) system greater than zero?