I haven’t played the game, so I’m not sure how accurate my help would be. It would be helpful to be able to look at some tooltips from these skills. But to my eye this looks like a talent / build system that’s fairly common in ARPGS.

My most basic assumption is that every so often you’ll level up and be able to pick one of these skills. They’ll provide some kind of effect which is tied to an active skill (Red, Blue, and Purple appear to be likely), or a passive bonus (Orange, Yellow, and Green I’d guesss).

The arrows are throwing me off a little bit because sometimes they point in both directions, and other times they appear to loop. Usually these might mark a pre-requisite skill, so if it shows [A] <-- [B] then that implies that before you can acquire A you must first acquire B.

If I had to guess, [A] <–> [B] implies either you can freely choose between A and B, or perhaps once you select A you must select B before you can select A again.

The loops feel weird though (notably in the yellow block). I guess that means that whatever skill you start with, you must then select clockwise from there.

There’s a great variety in how games will implement this sort of thing, but in general there’s usually a way to get a tooltip with a more complete description of what each thing does. Usually that would be by hovering over the icon, but some games include an encyclopedia of effects if they’re particularly involved.

The order in which you acquire these skills often influences your playstyle. Some people are going to prefer to get abilities that seem powerful quickly, and other people like to strategically synergize their build. For my part, I tend to prefer acquiring passive bonuses that increase my experience/luck/currency to more easily game the system.