Capital punishment is when a person is punished by death for committing a very serious crime. This type of punishment used to be very popular in Europe a long time ago, but nowadays it is illegal in many European countries.
Think about it like getting a time-out when you do something wrong, only the punishment is much bigger and can't be undone. If someone commits a serious crime like murder or treason, they might be punished by death.
But in Europe, many people believe that it is not right to take someone's life, even if they have done something very wrong. They believe that there are other ways to punish people, like sending them to jail for a long time or making them do community service.
Different European countries have different laws about capital punishment. In countries like France, Germany and Italy, the death penalty was abolished in the 20th century, which means that it is totally illegal.
In countries like the United Kingdom, it is still technically a legal punishment, but it is never used. This means that if someone was sentenced to death in the UK, it would be changed to life imprisonment instead.
So overall, capital punishment is mostly not used anymore in Europe because people believe it is not right to take someone's life, even if they have committed a very serious crime. Instead, they find other ways to punish people, like putting them in jail or making them do work to make up for what they have done.