A plain bearing, or more commonly sliding bearing and slide bearing (in railroading sometimes called a solid bearing or friction bearing[citation needed]), is the simplest type of bearing, comprising just a bearing surface and no rolling elements.A bushing might also be called a sleeve bearing. However, the term sleeve bushing would be redundant. Thus, a bushing is a bearing, but a bearing is not necessarily a bushing type. A bearing is the general term for something that allows relative motion between two components, surfaces, etc....