There are two main types of friction:
* Static friction: This force prevents an object from moving when a force is applied to it. It's the force you need to overcome to get an object to start moving.
* Kinetic friction: This force acts on a moving object, opposing its motion. It's the force you need to overcome to keep an object moving at a constant speed.
Friction is caused by microscopic irregularities on the surfaces of the objects in contact. These irregularities interlock and create resistance to motion.
