Definition:  The act, effect, or an instance of rubbing one object against another.[Physics/General] A resistance encountered when one body moves relative to another body with which it is in contact.

What does it do/what happens: Friction is the force resisting the relative motion of solid surfaces, fluid layers, or material elements sliding against each other. It’s thought as the opposite of slipperiness .There are different types of friction Dry Friction: resists relative lateral motion of two solid surfaces in contact. Fluid Friction: describes the friction between layers within a viscous fluid that are moving relative to each other. Lubricated Friction: is a case of fluid friction where a fluid separates two solid surfaces. Skin Friction: is a component of drag, the force resisting the motion of a solid body  through a fluid . Internal Friction: is the force resisting motion between the elements making up a solid material while it under goes deformation.

(Basic Properties) basic properties of friction have been described as laws. Her are three laws Amonton’s 1’st law: The force of friction is directly proportional to the applied load. Amonton’s  2’nd law: The force of friction is independent of the apparent area of contact. Coulomb’s Law of Friction: Kinetic friction is independent of the sliding velocity.

Bibliography:’’Friction’’,  www.Wikipedia.com, Wikipedia, 2010 
‘’ Friction’’ www.TheFreeDictionary.com , The Free Dictionary, 2010