A nanometer (NM) is a unit of measurement that is equivalent to one billionth of a meter. It is widely used as a scale for building tiny, complex, and atomic scale computing and electronic components - specifically in nanotechnology.
Techopedia explains Nanometer
Nanometers are used to measure the smallest things, usually those the size of an atom or molecule. This term is used in the context of miniature computing devices, such as integrated circuits (IC) and transistors embedded within a processor. Typically, the size of transistors on a semiconductor-based processor is calculated in nanometers. Each microchip can have transistors that are 100 nanometers wide and can accommodate more than 1 billion transistors within a single microchip die.