There are many types bearings in the market, such as metal pulley, pillow block bearing, deep groove ball bearing, etc.
In order to serve all these functions, bearings make use of a relatively simple structure: a ball with internal and external smooth metal surfaces, to aid in rolling. The ball itself carries the weight of the load—the force of the load's weight is what drives the bearing’s rotation. However, not all loads put force on a bearing in the same manner. There are two different kinds of loading: radial and thrust.
A radial load, as in a pulley, simply puts weight on the bearing in a manner that causes the bearing to roll or rotate as a result of tension. A thrust load is significantly different, and puts stress on the bearing in an entirely different way. If a bearing (think of a tire) is flipped on its side (think now of a tire swing) and subject to complete force at that angle (think of three children sitting on the tire swing), this is called thrust load. A bearing that is used to support a bar stool is an example of a bearing that is subject only to thrust load.
Many bearings are prone to experiencing both radial and thrust loads. Car tires, for example, carry a radial load when driving in a straight line: the tires roll forward in a rotational manner as a result of tension and the weight they are supporting. However, when a car goes around a corner, it is subject to thrust load because the tires are no longer moving solely in a radial fashion and cornering force weighs on the side of the bearing.