The amount of space available for labeling on most sound mixers is really limited, so sound people have developed a pretty standard set of abbreviations for marking which input is what.
Here are some of the most common:
Vox-Vocal
Kik-Bass Drum
SN-Snare Drum
Tom-Tom Tom
Sn-Snare Drum
Hat-Hi Hat
OH-Drum Overhead
Bs-Bass
Key-Keyboard
Gt-Guitar
Fid-Fiddle
Using these abbreviations means that almost any knowledgeable sound person can step up to the mixer and know what is going on.