The gravitational potential energy is the

Gravitational potential energy is the energy stored in an object due to its position in a gravitational field. It is defined as the negative work done by the gravitational force in moving an object from infinity to its current position.  

Infinity: This is a hypothetical point infinitely far away from the gravitational source (e.g., the Earth).

Radius r: This is the distance between the object and the gravitational source.

Therefore, the gravitational potential energy is the work done in bringing the object from infinity (where the gravitational force is negligible) to its current position (radius r), where the gravitational force is acting on it.