A power amplifier is an electronic device that increases the power of a signal, making it strong enough to drive speakers or other output devices. It takes a low-power input signal and boosts it to a higher power level, ensuring that audio or radio signals can be transmitted effectively over distances. Power amplifiers are commonly used in audio systems, such as home theater systems and concert sound systems, as well as in radio transmitters. They are essential for delivering clear sound and maintaining signal integrity, allowing for a better listening experience in various applications.