An AV receiver is more than just a simple amplifier. With its ever-increasing list of features, it has become the core of a good home theatre system. Their prime function is to amplify audio from a host of possible sound sources. They also route video signals from various sources directly to your TV.
Also known as the home theater receiver, this device is based on the principle of a stereo receiver. While the simpler stereo receiver has two channels of amplification, the AV receiver has at least five thus giving us the options for surround sound in formats of 5.1 up to 11.2. When surround sound is mentioned as 5.1 audio it means you have 5 speakers ( front left, front right, centre, surround left, surround right) plus the .1 is the subwoofer. 5.1 surround sound is the most common sold and installed.