A ball bearing is one of the most common components that is used to reduce the rotational friction. Ball bearings will have three parts of components working together to reduce that friction.
Ball bearings can be found in small and large motors, axles, electric fans and hard disk drives as well as the hubs of a motorcar wheels. There are various classifications and performance grades in ball bearings that help to choose the right ball bearings for optimum performance.
The three parts of a ball bearing are two bearing races and a set of balls in between them. When one of them rotates against the other, the balls rotate with it to facilitate a smooth rotation without creating friction and heat.
Text source: TT