The most popular use for a mixing console channel is for a musical instrument. This includes keyboards, guitars, basses, and other kinds of electronic instruments. These can be plugged directly to the channel or via an amplifier. They commonly connect via 1/4-inch phone plugs. If the board is powered (meaning that it has an amplifier unit in it), an amplifier is not necessarily needed.
Microphones are used to get sound from acoustic instruments like guitars, drums, and pianos. Of course, they're also used for vocals as well as amplifiers. There are a wide array of microphones on the market, and many studios have more than one since each has a different sound and tonal characteristics that may work optimally in different recording situations. The inputs used on these channels are balanced three-pin XLR inputs.
Reverb, delay, and chorus type effects are also used on the mixing console channel. These effects add a portion of the treated audio signal to the unprocessed or unaffected signal in order to create their effect.
Effects are usually routed through the mixing board via the send and return channels. Most nominal consoles have a send pre-fade control which is used to adjust the audio signal before the main channel gain control or fader, and post-fade control which adjusts the levels after the signal has been effected. In this way, the amount of effect on each individual channel on the mixing console can be manipulated by the using the channel's auxiliary controls.
Compressors, equalizers, expanders, limiters, and gates fall into the category of processors. Though effects process a signal as well, they do it differently. Processors treat the whole audio signal, not just a portion of it. Generally, they are connected through the individual channel itself or through an insert point on the console. Which effect is employed depends on the type of input in the individual channel.
Every channel needs proper studio cabling. The quality of the cabling that connects the mixing board is just as important as the board itself. Bad cabling can introduce noise into the channel like RF (radio frequency) signals and white noise, which are wholly undesireable.