A voltage regulator is a device that maintains a steady voltage within a prescribed range by automatically adjusting the output voltage to match the electrical load. Voltage regulators are commonly used in automotive and computer applications to ensure stable power supply. There are different types of voltage regulators including linear regulators, switching regulators, and zener diodes, with each having their own advantages and limitations in terms of efficiency, power handling capabilities, and design complexity. Voltage regulators work by generating a fixed output voltage magnitude that remains steady even if the input voltage changes.