What is positive and negative pressure for fans?

I'm planning to buy a mini-ITX PC sometime next week from PCS, you can check my thread on it here. I would appreciate any contribution to it.

I'll be going for a H100i V2 CPU cooler, two onboard GPU fans and three 120mm Apache fans (two at the front and another at the rear). So I'm looking at a lot of reviews and PC builds in the meantime and often comes across the term "pressure ventilation". Is this something I should be worrying about? Is this something I'm supposed to specify to PCS? I of course want the best exhaust and ventilation efficiency but how do I know which is best for my case configuration? What's the difference between them?

This video is quite good: https://www.youtube.com/watch?v=4NYHC3DXynM

I wouldn't worry about it a great deal, PCS seem to know enough about building PCs that whatever fan setup they arrange is likely to be more than fine for your PC.

Great video, thanks! The case I'll be sending in for my purchase is the "Corsair Graphite 380T" which has filtrated mesh panels at the front and both sides, meaning greater ventilation and breathability.

So I guess neutral pressure would be best for such a case, right? The two Apache fans at the front will draw in cool air, the rear fan will exhaust heat through the back and the rest will just leave through the side panels from the CPU and GPU coolers. That's roughly the same amount of exhaust as intake so... neutral pressure. And I guess for such a system, an open-air cooler would be preferable to the cooling style of the reference cards. Sound about right?

The difference is whether you blow more air in than you suck out (positive pressure) or whether you suck more air out than you blow in (negative pressure). I don't know enough to make an educated choice on which is better, but this might help https://rog.asus.com/5322012/overclocking/positive-or-negative-pressure-cooling/.