A differential amplifier is an electronic device that amplifies the difference between two input voltage signals while rejecting any signals that are common to both inputs. This makes it particularly useful in applications where noise reduction is essential, such as in audio equipment and sensor interfaces. Differential amplifiers are commonly used in operational amplifiers (op-amps), which are versatile components in various electronic circuits. They can be configured to perform different functions, including signal conditioning and data acquisition, making them vital in analog signal processing and communication systems.