An active filter is an electronic circuit that uses active components, such as operational amplifiers, to filter signals. Unlike passive filters, which only use resistors, capacitors, and inductors, active filters can amplify signals and provide better performance. They are commonly used to separate different frequency components of a signal, allowing specific frequencies to pass while attenuating others. Active filters come in various types, including low-pass, high-pass, band-pass, and band-stop filters. Each type serves a specific purpose in applications like audio processing, communication systems, and signal conditioning. Their ability to adjust gain and provide precise filtering makes them essential in modern electronics.