An audio-video receiver's main purpose is to take audio signals from various sources, such as a Blu-ray player, DVD player, or streaming device, and amplify them before sending them to speakers. It also allows you to control the volume, adjust the sound settings, and switch between different audio sources.

A stereo receiver is designed to amplify and distribute audio signals to two speakers, while an audio-video receiver can amplify and distribute audio signals to multiple speakers, including surround sound speakers. Stereo receivers typically only have analog audio inputs and outputs, while audio-video receivers have both analog and digital audio inputs and outputs. Additionally, audio-video receivers have video inputs and outputs, allowing them to connect to TVs and other video devices.

The most common number of channels in an audio-video receiver is 7.1. This setup consists of five main speakers (front left, front right, center, surround left, and surround right), two surround back speakers, and a subwoofer.

A subwoofer is a speaker that is specifically designed to reproduce low-frequency sounds, such as explosions, bass guitar, and drums. It helps to provide a more immersive and realistic surround sound experience by adding depth and impact to the sound.

Analog audio signals are continuous waves that represent the sound pressure at a given point in time. Digital audio signals are discrete values that represent the amplitude of the sound at regular intervals. Digital audio signals are less susceptible to noise and interference than analog audio signals, and they can be compressed to reduce their file size without losing any of the original audio quality.

HDMI (High-Definition Multimedia Interface) is the most common type of digital audio connection used in audio-video receivers. It is a single cable that can transmit both audio and video signals, and it supports a variety of audio formats, including Dolby Atmos and DTS:X.

Room calibration is a process that uses a microphone to measure the acoustics of the room and then adjusts the sound output of the receiver to compensate for any problems. This can help to improve the overall sound quality and create a more immersive surround sound experience.

Dolby Atmos and DTS:X are both object-based surround sound formats that use a height channel speaker layout to create a more immersive sound experience. Dolby Atmos uses a fixed height channel layout, while DTS:X allows for a more flexible height channel layout. DTS:X also supports more object-based audio than Dolby Atmos, which means that it can create a more realistic and immersive soundstage. However, Dolby Atmos is more widely supported than DTS:X, so it is more likely to be found in home theater systems.

A network connection on an audio-video receiver allows you to stream music and other audio content from online services, such as Spotify, Pandora, and Tidal. It also allows you to control the receiver with a smartphone or tablet using a dedicated app. Additionally, a network connection can be used to update the receiver's firmware, which can add new features and improve performance.

Passive speakers require an external amplifier to power them, while active speakers have a built-in amplifier. Passive speakers are typically more efficient than active speakers, meaning that they can produce more sound with less power. Active speakers can be placed anywhere in the room, while passive speakers need to be placed near an amplifier. This makes active speakers more convenient and versatile, but they can also be more expensive than passive speakers.

A crossover is a circuit that divides the audio signal into different frequency bands. This allows the different frequency bands to be sent to the appropriate speakers. For example, the low-frequency band is sent to the subwoofer, while the high-frequency band is sent to the tweeters. A crossover can also be used to adjust the volume of the different frequency bands.

Bi-amped speakers have two amplifiers, one for the low-frequency drivers and one for the high-frequency drivers. This allows for more precise control over the sound output of the speaker. Bi-amped speakers can also produce more power than single-amped speakers, and they typically have better sound quality. However, bi-amped speakers are also more expensive than single-amped speakers.

A tone control is a circuit that allows you to adjust the overall sound quality of the receiver. This can be used to compensate for the frequency response of the speakers, to adjust the volume of the different frequency bands, or to simply change the overall sound to your liking.

A stereo audio signal has two channels, one for the left speaker and one for the right speaker. A multi-channel audio signal has more than two channels, typically five or more. Multi-channel audio signals are typically used for movies and TV shows, as they can provide a more immersive surround sound experience. Stereo audio signals are typically used for music, as they are able to provide a good balance between the left and right speakers.

A remote control for an audio-video receiver allows you to control the volume of the receiver, change the input source, adjust the sound settings, and perform other functions. This makes it easy to control the receiver from anywhere in the room.