@keepthbeat, where did you even find the mixer tool? You're way ahead, so far as I can tell that will not come into play until week 3. But, the M stands for mute, the S for solo, PFL for pre-fader listen, and the knob is for panning. Last time around, the PFL button didn't work on the PWYM mixer, so it did nothing. This will all be explained in due time.
@CereBelle, check out the wikipedia article on mixing consoles , especially the area under "channel input strip." Basically, you have strips that run down the console (toward and away from you, if you're in front of it) -- each of these strips deals with a single input. First, furthest knob away from you, you have the preamp where you apply gain to the signal -- this is for calibrating the microphone volume to match the signal. After that, different things can happen but usually you'll have an EQ section with some knobs for adjusting the highs, mids, and lows etc (the details depend on the specific desk). Getting closer to you, there may also be knobs for aux sends, this is for sending the signal to a variety of auxiliary outputs (could be used for monitors, or outputs to another piece of hardware). Again this varies greatly from desk to desk depending on the complexity. There may be a section after that where you can also send the signal to "groups" or the master buss (main output), usually these are buttons or switches. There is usually the panning knob here for sending the strip to the left or right of the master, or for panning them to different groups. Finally, you have the fader, the slider you can use to adjust the volume of the signal coming out of the strip (after the preamp). The PFL button is for listening to the sound of the strip before the fader, so you can hear the pure sound of the preamp before the fader comes into play. Some of the aux sends may be pre-fader as well, but groups and busses are usually post-fader (so you can mix the different strips into a group using the faders). After all these strips, usually towards the right, there may be faders and knobs to control the overall levels of the aux sends, groups or busses, and master faders. Sometimes there's master EQ and a wide variety of other routing knobs, buttons, and faders.