WHAT IS ACTUALLY MEANT BY PURE ROLLING ?? ITS CONCEPT IS NOT CLEAR TO ME......PLZ HELP ME TO UNDERSTAND WHAT IT ACTUALLY IS ??

In pure rolling motion friction is required to start, stop, change the motion of a wheel.  Below we can see the frictional force necessary to begin motion, and get the wheel moving at a velocity v.  In pure rolling motion, friction causes the wheel to catch and stops the sliding and slipping motion; for example when a car spins its tires, slipping is taking place, thus the frictional force works to stop the spinning out and causes the tires to catch and begin pure rolling motion.

the frictional force, f, the force required to slow the wheel produces a torque which tends to decrease the angular velocity, w. (The normal and gravitational forces produce no effect because their line of action is through the center of rotation.)  However, the surface could not possibly have such an effect on the wheel once the wheel has achieved pure rolling motion and constant angular and linear velocity.