From Ents Wiki
The following articles are all about sound desks or mixing consoles.
In professional audio, a mixing console, or audio mixer, also called a sound board, mixing desk, audio production console, or mixer is an electronic device for combining (also called "mixing"), routing, and changing the level, timbre and/or dynamics of audio signals. A mixer can mix analog or digital signals, depending on the type of mixer. The modified signals (voltages or digital samples) are summed to produce the combined output signals.
Mixing consoles are used in many applications, including recording studios, public address systems, sound reinforcement systems, broadcasting, television, and film post-production. An example of a simple application would be to enable the signals that originated from two separate microphones (each being used by vocalists singing a duet, perhaps) to be heard through one set of speakers simultaneously. When used for live performances, the signal produced by the mixer will usually be sent directly to an amplifier, unless that particular mixer is "powered" or it is being connected to powered speakers. Among the highest quality bootleg recordings of live performances are the so-called soundboard recordings that are sourced from this mixer output to the speakers.
For more information on desks in general, consult the article Mixing console from Wikipedia.