Circular motion happens when an object moves around a point in space, never getting farther from it or closer to it. The distance from the center point is the radius of the circle.
In order to travel in a circular motion, an object must constantly change direction. Though its path forms a circle, the object is always moving tangentially to the circle. One tangent is simply interrupted by the next with each tiny directional shift.
When the object travels at the same speed around the point, it has uniform circular motion. According to Newton's second law, an object in uniform circular motion will also experience a force in the direction of the center point.