You might want to read up on "inline monitoring" to get a tutorial....the Mackie 8-bus (the analog version) documentation provides a pretty good explanation of this design. Basically, each channel strip can route 2 different sources through it at one time. The input can be tracked through the strips' preamp section, and then sent to the recording medium. At the SAME TIME, a different source (say, one of the tracks from the recorder) may be routed through the "monitor" section of the channel. Then, when you're ready to mix, the recorder may be switched to be the main inputs'source... It's like having 2 mixers in one desk. I know this simplifies things a bit, and many consoles take this basic design to extremes, but that's it for starters...It's really done for ergonomics and to minimize the "real estate" the desk takes up. In the "old days", there would be one side of the board used to track and mix the sources, and the "other side" would be another mixer taking the tape outs and mixing them to the monitors...this was called "split monitoring". The Brits had the splits, so to speak, while the Americans developed the inline approach, courtesy of a guy named Jeep.

Yeah and then he started a telephone company. Which was later sold to the Chrysler Corporation. Remember Rolls-Royce is now manufactured by BMW which has nothing to do with BMI, ASCAP or Andy Cap but might be related to Handy Cap?? Either way, I think my brain surgery has corrected my problems with associations with the AES and SPARS which can hurt if you get them in your fingers.

I've got blisters on my fingers!!
Ms. Remy Ann David