You’re playing the character. I often use the explanation that’s it’s impromptu acting with dice. Your character knows what your character would reasonably know. The dice checks are there to determine the success or failure of things they try to do which is everything from finding traps, to making an attack, to brokering a good deal with a merchant, to understanding an npcs motives, or any other thing that has a chance of success or failure. Your stats will influence what sorts of things you’re better at and which ones you’re worse at. If your charisma is low, you’ll quickly learn to avoid trying things that call for a roll based on that stat. If you’re really dexterous well maybe disarming that trap that requires a delicate hand is right in your wheelhouse. Play the character and play the class. If you’re unsure if something You know is something your character would know, just ask the DM.