Question

what is friction????

Answer 1

It's a force.

http://en.wikipedia.org/wiki/Friction

Answer 2

Friction
Definition:the resistance to the relative motion of surfaces of bodies in contact.
When two surfaces move over each other you can have friction. Rub your hands hard together and you will hear them rub and feel the warmth the friction between your two hands causes. When friction is high, two objects have more difficulty moving along each other’s surfaces. It takes more force to make them move. When friction is low, two surfaces can move easily across each other. Look at these examples and decide which has high friction and which has low.

http://rossmannellcomments.edublogs.org/2013/05/23/smooth-moves-motion-force-friction-push-pull-gravity-momentum-for-4km-and-4kj/