An absolute encoder is a type of position sensor that provides a unique digital code for each position of a rotating shaft. Unlike incremental encoders, which only indicate changes in position, absolute encoders retain their position information even when power is lost. This makes them ideal for applications where precise positioning is crucial, such as in robotics and industrial automation. These encoders work by using a series of concentric tracks, each representing a different bit of information. When the shaft rotates, a sensor reads the pattern of light or magnetic fields on these tracks, converting it into a specific digital output. This ensures that the exact position can be determined at any time, enhancing reliability in systems like CNC machines and elevators.