A mechanical bearing is an element used in machines. The basic idea and reason behind using a bearing is that things roll and rotate better than slide between each other. They are used in machines such as cars and help them function smoothly. Usually, there is a part which is the static component called stator and the moving component called the rotor. The rotor rotates in relative to the stator and the bearing provides it to function smoothly, with minimal friction as well as holds the bear of the rotational motion.
There are various types of bearings.
Ball bearing
Ball bearings, a type of a rolling bearing, are composed of inner and outer component in form of a ring, one small and one bigger.
Between them are spheres, or balls, against which one rings rolls/rotates against the other. These balls also bear a load of a particular motion.
Plain bearing
A plain bearing is considered as the simplest type of bearing. It allows motion of a journal (the part of the shaft that is in contact with the bearing) inside a hole.
They have a high loading capacity and are popular due to its low cost and and weight.