Well, the basic idea behind patching is that you're taking what may be the random and confusing mess of
dimmer numbers and addresses, and ordering them in a way that makes sense to you by assigning them channels. So your front light might be dim# 321 432 500; but you can assign those to channels 1,2,3.
Honestly though, with newer boards it is not as necessary as it used to be. I will patch my fixtures in groups by type because that's the easiest way, but once I
build the 2d
visualizer/
magic sheet, I all but forget about the
channel numbers. I can drag and
drop selection buttons on the touchscreen to wherever makes sense.
Bottom
line is you are organizing your lights and board so that when the director/designer says "I need a pool of blue light DSL" you can quickly and efficiently make that happen.