The four main types of bearings are ball bearings, roller bearings, plain bearings, and thrust bearings. Each type is designed to address specific load-bearing requirements and operational conditions in various machines and equipment across different industries.

The primary function of a bearing is to enable the controlled transfer of loads and motion while minimizing friction and wear. Bearings achieve this through the use of rolling elements, such as balls or rollers, or through sliding surfaces, depending on the specific type of bearing. By doing so, bearings help to maintain the integrity and alignment of rotating shafts, axles, and other mechanical components, ensuring smooth and efficient operation of the machinery.