Any net force causing uniform circular motion is called a centripetal force. The direction of a centripetal force is toward the center of curvature, the same as the direction of centripetal acceleration.
It is important to understand that the centripetal force is not a fundamental force, but just a label given to the net force which causes an object to move in a circular path. The tension force in the string of a swinging tethered ball and the gravitational force keeping a satellite in orbit are examples of centripetal forces. Multiple individual forces can even be involved as long as they add up to give a net force towards the center of the circular path.
A moving object always travels in a straight line unless a force acts upon it. When a weight is spun round quickly on a string, it moves in a circle. This means that a force must be making the weight change its direction all the time. As the object spins you can feel the string pulling on your fingers. The string also pulls on the weight. It is this pull that makes the weight change its direction — a ‘centripetal’ force.
When you sit in a ride at a funfair, or in a car moving fast around a roundabout, you will also feel the effects of centripetal force. As the car turns, it pulls you with it, exerting centripetal force on you as it does so.