Bearings are friction components that carry loads as they come into contact with and move relative to another part. Motion can be sliding or rotating. There are basically two types of bearings: plain bearings and rolling bearings. Other types of bearings include fluid bearings that support their load on a thin layer of gas or liquid. Magnetic bearings that use a magnetic field to carry loads; hinge-like flexible bearings in which the load is supported by a curved element; jewel bearings used in timepieces.

Plain bearings, also known as bushings, bushings or sleeve bearings, are usually cylindrical and contain no moving parts. Standard configurations include cylindrical bearings for radial loads, flanged bearings for radial and light axial loads, thrust and flanged washers for heavy axial loads and sliders of various shapes. They can also be custom designed, including special shapes, features (deep grooves, oil holes, notches, protrusions, etc.) and dimensions. Plain bearings are used for sliding, rotating, oscillating or reciprocating movements. In sliding applications they are used as plain bearings, bearing strips and wear plates. In these applications, the sliding surface is usually flat, but can also be cylindrical, and the motion is always linear, not rotational. Rotational applications involve cylindrical surfaces and one or two directions of travel. Oscillating and reciprocating applications are flat or cylindrical, but travel in both directions. The structure of the plain bearing can be solid or split (wound bearing) for easy installation. It is important to match the bearing to the application. High loads require bearings with larger contact area and high load carrying capacity. Bearing designs with solid lubricants can operate at higher temperatures than oil/grease lubricated bearings. High-speed applications require special lubricants to minimize heat build-up and friction. Plain bearings are manufactured with different constructions, and the choice of product depends on the operating conditions and performance requirements of the application.