Great question! Centrifugal force occurs when an object is forced to travel along a non-straight path such as around a center of rotation. Consider for example a swinging ball attached to a peg by a string. As the ball is moving around the peg, it wants to escape this orbit by traveling straight, but the string is strong and keeps it rotating around. This tendency to travel straight is called inertia. From the peg’s point of view, the force that the ball is pulling on the string is centrifugal force. From the ball’s perspective though, the peg is pulling on the string to keep the ball rotating around. This is called centripetal force. The two forces are equal and opposite of each other, just as Newton’s Third Law of Motion says.

Centrifugal "force" is the result of something called the "conservation of momentum". Anything moving will continue moving in the same direction unless acted on by a force. Anything moving in a circle will need force constantly acting on it to change its direction so that it doesn't veer off in a straight line. However, just because one thing is turning due to force doesn't mean that things on or in it are turning as well - unless the sides of the thing doing the turning is also exerting force on its contents (which it must, if they are to stay inside). This process - the tendency of things to veer off or the force required to keep them from doing this - is what we know of as centrifugal force.