The term bearing comes from verb to “bear” the bearing is a machine element that allows one part to bear another.
The bearing is any of various machine elements that constrain the relative motion between two or more parts to only desired type of motion. It’s promotes to allow the free rotation around fixed axis or free linear movement. It may also prevent the motion, such as by controlling the vector of normal forces.
Bearing may be classified according to the motion they allow and principle of operation as well as by the direction of the applied force they can be handle. The most sophisticated bearings, for the most demanding applications, are very expensive, highly precise devices, whose manufacture involves some of the highest technology known to human kind.