Mic Level is the wimpy kid everyone picks on but is also smart because he finds other kids to back him up. (lowest level)
Instrument level is the kid who does good in school,plays a sport, and is generally mentally balanced. (middle level)
Line level is the jock that everyone wants to be because he/she pushes through any obstacle. (highest level)
You can plug in 2 instruments on inputs 1 and 2, the rest require a DI box.