There are different types of friction, including:
* Static friction: This acts on objects at rest, preventing them from moving. It's the force you need to overcome to start an object moving.
* Kinetic friction: This acts on objects that are already in motion, slowing them down.
* Rolling friction: This is the friction that occurs when a round object rolls over a surface. It's usually much less than sliding friction.
Friction is caused by the microscopic irregularities on the surfaces that are in contact. These irregularities catch on each other and resist movement.
