basically, insert point
a place in the signal path where you can insert a piece of gear
usually a compressor
aux send
a split of the signal that can be sent somewhere else
usually reverb
busses
where the signal leaves the mixer
usually you send to the master buss (stereo buss, 2 buss, 2mix)
but you can send a collection of things to subgroups
if your mixer has 8 busses, you could send all the drum channels to busses 1 and 2, then the buss faders for 1 and 2 would control the overall level of your drum kit
feel free to ask any questions
once you understand these basic concepts, the door will open and youll be able to look at it in a very logical way