The word "tracks" has several possible meanings, as do most media terms.
OBS's Tracks are fed only from the Advanced Audio Properties. Then you choose in Settings -> Output which of those you want to stream and/or record. Each track contains the entire channel count that OBS is set for: mono (1), stereo (2), 5.1 (6), etc.
Tracks in general are simply independent streams of "something". A 24-track audio recorder, for example, records 24 mono waveforms simultaneously and separately. Stereo takes 2 of those, 5.1 takes 6 of them, etc. Play them simultaneously in sync through a mixer, and you can produce a stereo track (different definition again) to release commercially. A video editor will even have video tracks that work in much the same way.
So what do you actually mean?