Totally noob questions d1800 btc mobo

So I just bought this mobo (D11800 BTC)and psu.
and I am plugging this up and I see POUT1 - POUT3 och PWR1-3 etc on the side and
I am kind of curious what those are, as I never never meddled with this before only
ever built “normal” computers, I am wondering, are they necessary to use as I plug in power
to each graphics cards in the graphics card itself (rx 580 8gb)