Can someone explain what MINUS 12 volts supplied by a power unit is all about?

Hi, yeah...i'm sure this question is super-ignorant, ultra-beginner level, and i'm showing my drastically limited understanding of electrical devices...but here goes

Why does my power supply module (which is the uZeuz power unit of the Tiptop Happy Ending 19" rack kit, but I presume this applies to many such units) have one supply for ribbon cable that is +12v and another for -minus 12v

I'm powering my modules off the + 12v, but can someone explain what the minus - 12 v is all about, and what that would be used for?

thanks T

In electrical circuits you always have a +Plus and a -Minus, think of it as turning on a light swtch to join the two and you get light.
Connecting your power cables the correct way around is important.

Older thread discussing -12, 0 & 12V

Thanks, also noting that Doepfer modules probably don't have reverse polarity protection, so i've probably been lucky (nothing blown at this point)

Eventually i messaged Tiptop's tech support asking about what modules should be attached to the positive bus, what should be attached to the negative.
They just said that it doesn't matter, because all of the busses supply all of the types of current.
I've certainly had no blow outs or functionality issues with any module. I did dutifully connect the one module i have that says it wants neg to the neg bus. Why not? But then again, why? since all busses carry all polarity combinations?
As a person who likes to imagine i'm vaguely logically minded (albeit , i admit, with limited knowledge), this does leave me wondering why the different busses are defined as positive and negative polarity? Whatever the answer is to that (if there is one), it certainly isn't to do with the polarity of then current that the busses deliver, since all the busses deliver currents of all polarity.
Guess I may never know.
And it apparently makes no practical difference

The bus current is polorised +/-
Pretty sure their modules will be made to correct their own polarity whichever way you plug them in.
Not all manufacturers do that.