Friction is the property that objects have which makes them resist being moved across one another. Friction has many uses such as it makes the wheels of a locomotive grip the rails of the track. It allows a conveyor belt to turn on pulleys without slipping. It keeps from cars to side on the ice if they have 4 wheel drive.
Friction also has disadvantages such as it produces heat that may cause objects to wear This is why oil and other lubricating liquids are used to fill spaces between moving machinery parts. The lubricating liquid reduces friction and makes the parts move more easily and produce less heat.