Friction causes a moving object to slow down. Friction applies force in the opposite direction of the existing path of the object. A baseball player sliding into a base will slow down because of the friction between the ground and his body.
Scientists measure friction based on the materials that are rubbing against one another. Velcro against cloth has a high coefficient of friction, which is a measurement of the ease with which two objects move when in contact with one another. The higher the coefficient of friction, the more friction exists between the two objects. For example, a nonstick coating on a pan, such as Teflon, has a much lower coefficient of friction than a pan without such a coating. This allows the pan to be cleaned very easily.
The presence of additional substances influences the force that friction can exert on an object. A car braking to a stop on a dry road has fewer difficulties than a car driving during a rainstorm. The presence of liquid interferes with the contact that the brakes make with the rotor on the car wheels, resulting in slower braking speed. Water interferes with the contact between the tyres and the road as well, reducing the work of friction.