What is a mixer?
A mixer, in its purest and simplest form, combines or meshes an array of inputs into a few controllable outputs (hence the name, MIXer). It is pretty much universal that mixers will have at least a volume control on the output. The vast majority will have volume or "level" controls on each input, or "channel." A great many still will have a variety of controls on each channel, from gains or trims to EQ and aux'es and buses and PFL's and more; don't worry though - I will go through each of these at least briefly.
When a new sound guy looks at a mixer for a large church, per se, he may feel overwhelmed by the oceans of knobs that may or may not be there. But here,I will explain what these knobs do, and you will actually find them to be overwhelmingly simple.
The first thing you need to know is that I will be dealing with moderate to large mixing desks and sound boards, with at least 10 channels (available inputs) or more. These are what you will see if you want to "run sound" for a church or venue or record music of bands, etc.
Step 1: Channels
Simply look at one of the black circle inputs (XLR's for microphones and snakes), then follow the column of knobs straight down. This is a channel strip.