A linear regulator is an electronic device used to maintain a constant output voltage from a varying input voltage. It works by dissipating excess voltage as heat, ensuring that the output remains stable even when the input fluctuates. This makes linear regulators ideal for applications where low noise and simplicity are important, such as in power supplies for sensitive electronics. Linear regulators come in various types, including low-dropout regulators (LDOs), which can operate with a small difference between input and output voltage. They are commonly used in battery-powered devices and consumer electronics due to their ease of use and minimal external components required for operation.