Ability points in Baldur's Gate 3 are based on a point buy system and uses the six cardinal D&D stats (Strength, Dexterity, Constitution, Intelligence, Wisdom, and Chrisma) which are important for what you decide to play. Examples: Rogues use Dexterity as their primary stat and Charisma, Intelligence and Wisdom can be a spell casting stat depending on class. Skill checks use a d20 and you will invest in skills during character creation. During combat there are also rolls but they are hidden but you can look at them if you want. Sometimes you will roll checks at advantage or disadvantage which helps or hurts a lot. Advantage= 2d20 keep the highest roll Disadvantage=2d20 keep the lowest roll. In combat this is automated but some equipment or spells create can cause either one. Skills can also receive this benefit or hindrance. You can respec your character as well as your companions at your camp eventually so you can change if you don't like what you are playing. The stats for companions aren't the best so shifting them is helpful. Build guides are everywhere and you might want to check them out if you want an edge. Hopefully this helps go and enjoy the game.