Okay, imagine you and your friend are playing a game. Your friend does something bad and you want to punish them for it. But you also want to make sure the punishment is fair and not too harsh.
Now let's say that punishment is taking away your friend's favorite toy. But you both have to decide if this is a good punishment or not. That's what a group of adults did when they tried to figure out how to punish people who did really bad things, like killing someone.
One of the ways they decided to punish people was the death penalty, which means the person who did something really bad would be killed as punishment. However, some people thought that was too harsh and even unfair, especially since not everyone who did a bad thing got the death penalty.
So, in the case of Gregg v. Georgia, the court had to decide if using the death penalty was constitutional, which means it followed the rules of the United States government. They decided that as long as there were certain rules and procedures that were followed fairly and consistently, the death penalty could be used.
Think of it like this - if you and your friend decide that if someone breaks a rule then they have to go to timeout for 5 minutes. But you also decide that there are certain rules for when timeout is given, like you have to warn the person first and only put them in timeout if they keep breaking the rules. Then, using timeout as a punishment is okay as long as you follow those rules.
So, the court said that if the government follows certain rules and procedures, then using the death penalty is okay. But they also said that if the rules aren't followed, then the death penalty would be unconstitutional.