Plain bearings are composed of two parts. On one hand, there is the fixed part, which bears the loads, known as the support, and on the other, the area that gets worn; in other words, the one that is in contact with the moving element: the bush.

With the purpose of minimizing the losses generated by the bearing friction, material pairs with low friction coefficient is generally used, or a lubricant is added between the parts: solid – graphite or Teflon -, liquid – oil – or gaseous – pressurized air.

A plain bearing, or more commonly sliding bearing and slide bearing (in railroading sometimes called a solid bearing, journal bearing, or friction bearing[citation needed]), 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 and lightweight, and they have a high load-carrying capacity.