A shift register is an electronic circuit used to store and move digital data. It works by shifting bits of information in a specific direction - left or right - each time it receives a clock signal. Shift registers are commonly used in computers and digital systems to organize, transfer, or manipulate data efficiently. They play a key role in serial-to-parallel or parallel-to-serial data conversion, temporary data storage, and digital signal processing. Their design enables the sequential movement of data, making them essential for tasks like data transmission, data buffering, and timing adjustments in various digital applications.