Guys, I have never played or seen anyone play D&D in my life, but I still enjoy the memes for some reason. I’ve seen people name powers, roll a dice and then scream in agony or joy… But I never know what the hell is going on. I know a higher number is better but I don’t know what is done with the number. Can someone explain?

Like, I say “ice shield” and I roll a 15. Then what?