Centripetal” is a word (apparently coined by Isaac Newton) meaning “center-pointing.”
“Centrifugal” means (roughly) “center-fleeing,” or pointing AWAY from the center (so, radially).
So the words simply refer to directions, and the “center” implies that the forces act in reference to motion in a circular path. Such motion is very common: in the case of a rotating rigid body (i.e., solid object), the motion can be described as a combination of (1) a movement through space of the center-of-mass plus (2) circular motion of all the particles in the body about an axis passing through the center of mass.
The net force on ANY mass moving in a circle at constant speed is a centripetal force. If the mass’s speed is changing along the circular path, there must be a tangential force in addition to the centripetal.
An example of a centrifugal force would be the force ON THE STRING when a stone tied to the string is whirled in a circle. The force on the stone is a centripetal force, and the third-law reaction force exerted on the string is a centrifugal force.
