Capital punishment is when someone is punished by being put to death by the government. It is a serious punishment that is used in some countries when someone has committed a very bad crime like murder or treason.
Imagine you are playing with your toys and your sister comes and takes away your favorite toy without asking. That might make you very angry, but you can't hurt her or take something away from her because that would be wrong.
In the same way, sometimes people do really bad things, like hurt other people or steal things. When they do this, they go to a court where a judge and a jury decide if they are guilty or not. If they are found guilty of a really bad crime, like murder, the judge might decide that they deserve the most serious punishment of all- being put to death.
The government has rules about how they can put someone to death, and it usually involves a special kind of injection or electricity. But some people don’t think it's fair to use the death penalty. They think that no matter what someone has done, they deserve to keep their life. Others think that capital punishment can be a way to deter people from committing really bad crimes.
So, capital punishment is when the government punishes someone by making them die because of the very bad things they did. It’s a serious decision that has to be made with a lot of care and thought.