Mackie Mixer Moves

As a vocalist and keyboard player, I own a Mackie mixer. It's fairly new but has only 6 channels and is not the multilayer-ed "beast" that Tom Beyer brought into the class for us to work with.
Mackie makes these large analogue mixers with functionality in mind- as part of a PA sound reinforcement system, as well as a live audio and video recording machine - where there will be monitor and main speaker mixes, head phone mixes and video. One aspect of this Mackie that I am not so sure of is Bus Channels so, I went searching:
Bus: compute data channel: a channel or path for transferring computer data, especially between the central processing unit and a peripheral device. Therefore, having these BUS channels means that any tech setup where data will be controlled via computer, will need an analogue mixer with BUS Channels - boy, I hope that's correct thinking!

The class has used this Mackie three times for different setups and there is something so beautifully powerful - and yet so simple about setting up for Audio --it is the most straight forward; Three mics, three XLR cables , female to male etc. three boom stands and
three input channels at the back of the mixer. The straight line approach, although not necessarily the one that will work in every day life, is the one that works in audio. From A to A to A to A etc.... keep things uniform. Number 1 mic into #1 Cable into #1 Input at the back of the mixer, and then controlled by the #1 Chanel.