Nanometer in CPU refers to the size of its manufacturing process, also known as process technology. A nanometer is a unit of length equal to one billionth of a meter. In CPU manufacturing, nanometers are used to represent the size and distance of electronic devices.
The smaller the number of nanometers of the process technology, the smaller the device manufactured, the higher the density of the transistor, which usually means higher performance and lower power consumption.
For example, the advancement of process technology from 14 nanometers to 10 nanometers means that the number of transistors increases relative to the same chip area. Therefore, the application of nano in CPU is to describe the technological changes and advances in CPU manufacturing.