bearing technology - rolling element bearing

A rolling-element bearing is a bearing which carries a load by placing round elements between the two pieces. The relative motion of the pieces causes the round elements to roll with very little rolling resistance and with little sliding.
Most rolling element bearings use cages to keep the balls separate. This reduces wear and friction, since it avoids the balls rubbing against each other as they roll, and precludes them from jamming
Even though some other kind of bearings are better in one or another specific attributes, many people think that it gives a pretty good tradeoff between cost, size, weight, capacity and durability. Therefore, it is one of the most widely used in machinery design
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bearing technology - plain bearing

A plain bearing, also known as a plane bearing, is the simplest type of bearing, comprising just a bearing surface and no rolling elements. Therefore the journal (i.e., the part of the shaft in contact with the bearing) slides over the bearing surface. The simplest example of a plain bearing is a shaft rotating in a hole. A simple linear bearing can be a pair of flat surfaces designed to allow motion; e.g., a drawer and the slides it rests on or the ways on the bed of a lathe.

Plain bearings, in general, are the least expensive type of bearing. They are also compact, light weight, and have a high load-carrying capacity. Read more