Plain bearings are simple mechanical components that allow for smooth motion between two surfaces. They consist of a shaft that rotates within a cylindrical sleeve, often made of materials like bronze, plastic, or steel. These bearings reduce friction and wear, making them essential in various applications, from automobiles to industrial machinery. Unlike rolling element bearings, plain bearings do not have balls or rollers. Instead, they rely on a thin film of lubricant to minimize contact between the surfaces. This design makes them cost-effective and easy to maintain, but they may not handle high speeds or heavy loads as well as other bearing types.