It's a fantasy role-playing game.

DM: You are Grog Strongjaw, a goliath barbarian . You are the member of the famous group of adventurers. Previously,  Some of them splintered off to try and acquire the goods that were taken from his store, however they apparently had already been stolen from the location they were being stored in, or been delivered already, they're uncertain as to what became of them. But they get the sense that it was probably best that they chose Gilmore over the gold, at first glance.
DM: All right, (wyvern noise) in there, and this one stays there and is going to unleash upon you, Grog. It's going to bite and tail attack against each of you with the stinger against you, Grog. That is a 21 to hit?
Player: Hits.
DM: And natural 20 on the stinger, okay.
Player: Well, I have resistance against poison, so that helps.
DM: That does help, actually, so it'll just do regular poison damage against you. So you take 11 points of piercing damage, reduced to six from the bite. And the stinger deals-- That's 12 points of piercing damage, reduced to six as well.
Player: Okay.
DM: The stinger, however, I need you to make a constitution saving throw.
Player: All right. Ugh, 12.
DM: That's a failure. Actually, it would have been an additional 12, because it was a critical hit on the pierce, so you take 12-- so a total of 18 damage so far, and then, as part of the poison, you take 48 points of poison damage. Because you have resistance, that is reduced to 24.
