I think this person means "What situation were you in when you folded your kings against aces?"
In my case, I have never done this. Mathematically speaking, you should never fold kings preflop. However we have all seen people do it on tv and in videos, but it's very rare for someone to do it and be correct. I wish they would show a video on the wsop tv shows showing people folding hands like that incorrectly.
This mathematically speaking comment is wrong. Mathematically speaking, you need to be very sure they have AA, but if your range is 60% AA, 30% AK, 10% QQ, you should fold (.8*.6 + .3*.3 + .1*.2 = .59 = you lose 59% of the time, and if you're 80% sure they have aces, it's an easy fold, those instances just basically never come up. Basically you're right, but mathematically it can be correct).
As for the OP, the only time you should ever fold KK or AA (unless it's KK and you're extremely sure you're up against AA) is in a tournament, where you're near the lower end on the bubble and there's a multi-way pot. Say a tournament pays the top 27 people at least $100. You're in 17th place with 30 left. You pick up AA and when it gets to you 3 people are already all-in and have significant stacks that either you are out or close to out if you don't win. AA against 3 random hands is only 60% to win, and the hands won't be random, they will be better than random. So almost half the time you bust out with nothing, where if you just check-fold your way to the money you'll win $100+. It all depends on the situation though. If a quadrouple up here gives you a shot at $10,000 it may be worth it. I would never fold KK or AA in a cash game unless I am playing against extremely tight players who get scared when KK faces resistance.