Just out of curiosity, as I genuinely don’t know, but what exactly does advantage/disadvantage do? I recognize that it makes things harder or easier to hit, but what is the math. Does advantage give you say a +2 to hit +5 etc. it may be that this was explained somewhere, but I must have skipped over it if so.
When you have an advantage or a disadvantage, there are 2 rolls with the D20 instead of 1.
When you have an advantage the best result is used in the maths.
When you have a disadvantage, the worst is used.
It the best bonus/malus to your %to hit in D&D and there are many spells, class features or "tactics" to have an advantage/give a disadvantage.
here's a link that show the influence it has on your %to hit.
https://statmodeling.stat.columbia.edu/2014/07/12/dnd-5e-advantage-disadvantage-probability/I.E you have 55% to roll a 10 without advantage/disadvantage (if you only roll 1 dice)
... you have 80% to roll a 10 with advantage (if you roll 2 dice and keep the higher result)
... and 30% with a disadvantage (if you roll 2 dice but keep the lower dice)
In other word this is the main reason why you'll try to make smart moves in combats.
That's why many players hate those 2 rules : In BG3 you just have to go behind or go higher (this doesn't exist in D&D)
It completely removes a huge part of the tactical value of the game because you never have to find a smart way to have the best bonus.
