There are two main types of friction:
* Static friction: This is the force that prevents two surfaces from moving relative to each other when they are at rest. It acts in the opposite direction to the force trying to start the movement.
* Kinetic friction: This is the force that opposes the motion of two surfaces sliding over each other. It acts in the opposite direction of the motion.
Friction is caused by the microscopic irregularities on the surfaces of objects. When two surfaces are in contact, these irregularities interlock, creating a resistance to movement.
