A demultiplexer is a digital device that takes a single input signal and routes it to one of several output lines. It essentially performs the opposite function of a multiplexer, which combines multiple inputs into one output. Demultiplexers are commonly used in communication systems to direct data to specific destinations based on control signals. In a typical setup, a demultiplexer has one input, multiple outputs, and control lines that determine which output will receive the input signal. This allows for efficient data management in systems like telecommunications, data routing, and computer networks, where directing signals accurately is crucial for performance.