You can press the select button in 1 of the formation menus and you'll get a detailed explanation. You don't need to bother though it won't really help you with anything.
I can't remember the exact letters but the white cards are B for balance, the orange cards are P for player (which you can turn on/off), and green cards are S for skill, something along those lines. Then the cards start getting a number after them. For example, Reaction is S01 cuz it's the 1st of the green cards, and the list goes on. The slashes also serve the same purpose as the letters.
I think the whole point is when you're comparing 2 different players' skill page, 1 of them has a small view so you only see letters and numbers. I guess it would be useful if you can remember every single number but it's too much to remember for me lol.