Friction. This is when two objects rub together. There are three different types of friction. This resistance works against motion and will act in an opposite direction. One is dry friction, which is when two solids are touching each other.
Next, is rolling friction, which is when a round surface, like a ball. rolls over another surface. Lastly, there is a fluid friction, which will involve either fluid or air. Some friction is vital to our everyday lives. For example, when a car brakes, the frction between the brakes are what helps us stop.