is a display of humour in which words are used within a concrete and well-defined narrative structure to make people laugh and is not meant to be taken seriously, but it could be. Joke should has a point. The most common way of saying a joke is oral way, but you can also write and read a joke, but the intonation is often very important, to make the whole joke funny.
Some people earn money via making a jokes. They can make them or just present them in front of the people. They are called stand-up comedians. The most popular are for example: George Carlin, Louis C.K., Dave Chappelle, Eddie Murphy or Jim Carrey.