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The centrifugal force in a rotating object is a fictitious force caused by the inertia of the object. Naturally, at any given point, the object wants to travel in a straight line, so its "desired path" is a straight line tangent to the circle in which it is rotating. Thus, rotating objects tend to move outward.
For example, let us say that a ball is tied to a post by a string and is rotating with uniform circular motion.
From an inertial frame of reference, the centripetal force, which is the tension in the string, is the only force acting on the ball (we are ignoring gravity for this example).
On the other hand, let us taking a frame of reference that is rotating with the ball, such that the ball appears stationary. (For example, you may take the reference frame of the ball itself, or that of a child running around the post.) Now, the centripetal force is acting on the ball, but the ball is not moving! We must introduce a fictitious force pulling the ball outward to satisfy Newton's Laws of Motion. This force is our centrifugal force.