Friction is a force that resists the movement of one object over another object. It is caused by the roughness of the surfaces in contact with each other.
The three main types of friction are static friction, kinetic friction, and rolling friction. Static friction occurs when two objects are not moving relative to each other, kinetic friction occurs when two objects are sliding past each other, and rolling friction occurs when an object is rolling over a surface.
Friction acts in the opposite direction of motion, causing objects to slow down or stop. It also causes objects to heat up, as the energy of motion is converted into heat energy.
The amount of friction between two surfaces is affected by the type of surfaces in contact, the force pressing the surfaces together, and the smoothness or roughness of the surfaces.
Friction can be reduced by using lubricants, such as oil or grease, between two surfaces. It can also be reduced by using smoother surfaces and reducing the force pressing the surfaces together.