A joke is something said, written or done to make people laugh. There are many kinds of jokes; they can be questions with surprising answers or stories with unexpected endings. The humour of a joke comes from the surprise.
Jokes can be about anything. Jokes can be found anywhere: on the Internet, in books or heard from friends. Some jokes are about groups of people and can hurt people's feelings, for example if they are racist, homophobic or sexist.