What is the difference between an object being at the point of toppling and an object being at the point of slipping? Does friction take on its maximum value in both cases, since there is relative motion between the two objects? And in general, what does rolling without slipping and slipping without rolling mean? Please keep in mind that I'm only in high school. 
 A: Consider a block kept on a rough table having the limiting value of friction K.Generally when you solve a problem it is adviced to consider the object as point mass. Toppling is generally considered for rigid mass system.Consider that you apply a force F to that block  anywhere at a distance L from its centre of mass. So when you apply force F which is less than K , limiting value of friction , then their is Normal shifting which means that the normal force shifts towards the direction of force applied from its centre of mass. If you constantly increase the force F keeping it less than K then at certain point of time the normal force will pass through the rightmost edge of the block. This is the condition of toppling that is the block is just about to topple.If the force applied equals the limiting friction K before the normal force reaches the edge then this condition is sliding condition that is the block is just about to slide from its place.
                          As far as rolling is considered if the point of contact of the roller and the surface does not have  any tangential acceleration then this is refered as rolling without slipping.In these cases the roller has only centripetal acceleration and work done by friction is zero. 
Slipping without rolling means the roller has only translational kinetic energy .The point of contact has tangential acceleration only.The angular acceleration of the roller is zero in this case.
