Sometimes, it is hard to distinguish a power from a skill. For instance, in some games, psychic powers might be something anyone can learn, but grant powers beyond an ordinary person's. In another game, quickly drawing a weapon might be defined as a binary feat or advantage.
A general definition of a power might be an advantage that gives a character a capability beyond a normal person. Thus, superpowers, mastery of the Force, or a style of martial arts might all be powers in this general sense. While powers might be learnable and have some relationship with a skill, powers are not simply a trait someone can learn more and more about. Rather, a power gives a character a new capability.