An audio amplifier is an electronic device that increases the power of audio signals. It takes a weak audio signal, such as from a microphone or musical instrument, and boosts it so that it can drive speakers or headphones. This allows for louder sound output without distortion, making it essential for music systems, public address systems, and home theaters. Audio amplifiers come in various types, including class A, class B, and class D, each with different efficiencies and sound qualities. They can be found in standalone units or integrated into devices like stereos and televisions.