What is the origin of the idiom "punch line" and when to use it?

The idiom "punch line" is thought to have originated in the United States in the early 20th century. The first known use of the phrase in print was in 1916, in a newspaper article about vaudeville (a form of popular entertainment that was popular in the United States from the late 19th century to the early 20th century). This expression is now used to describe the funny part of a joke, story, or speech. It can also be used to describe the main point or conclusion of something.