Hi Will,
I think your teacher meant centrifugal force. It is true that centrifugal force is not a real force.
Centripetal is a real force - this is a force acting towards the centre of the rotation. When you are inside a spinning drum, the centripetal force is the force from the inside of the drum pushing you towards the centre, preventing you from flying outside the drum. Centrifugal force, on the other hand, is commonly thought to be the force that is pushing away from the centre and against the outside of the drum, but really there is no such force (your body just naturally wants to continue along its original straight line path but the outside if the drum prevents that with centripetal force.