What is Friction?

Friction, a Speed killer:

Friction is the force resisting the relative motion of two surfaces (mostly solid or fluid) sliding against each other. There are several types of friction like:
1) Dry friction
2) Lubricated friction
3) Skin friction etc.

So basically friction is something that opposes the motion of  an object.

The thing we are interested in is studying the motion of objects when there is no friction at all (we dis-regard air resistance).

Therefore, the key question we are going to answer is: "How is the motion of objects when there is no friction?"