BG3 uses D&D fifth edition rules, and the game is set in the Forgotten Realms, which is the official setting for D&D right now. That being said, that can be a lot to get into, and the BG3 tutorial is trash. For character creation you might just want to pick one of the origin characters. Creating a custom character can take a good long while, even if you know the rules already. The origin characters have most of the basic classes covered and will give you a feel for the game. If you want to change it up, there is a way to change your class and stats partway through act 1. That will at least get you in the game and playing, where there are tooltips that pop up.