In terms of its role should be support, that is, the literal interpretation is used to bear the shaft, but this is only part of its role, and the essence of the support is to be able to bear radial load. It can also be understood that it is used to hold the shaft. Automatic selection of bearings is included. It is to fix the shaft so that it can only rotate, and control its axial and radial movement. The motor can’t work at all without bearings. Because the shaft may move in any direction, and the motor operation requires that the shaft can only be rotated. In theory, it is impossible to achieve the role of transmission, not only that, the bearing will also affect the transmission, in order to reduce this impact on the bearing of the high-speed shaft must achieve good lubrication, some bearings themselves have lubrication, called pre-lubricated bearings, and most bearings must have lubricating oil, responsible for high-speed operation, due to friction will not only increase energy consumption, What is more terrible is that it is easy to damage the bearing. The argument that sliding friction is transformed into rolling friction is one-sided, because there is something called plain bearings.