A clever play on words, often used for comedy. The play on words often use similar sounding words or homonyms to replace words that would normally be in the sentence. Another form is when a word with a double meaning is used to relate to a different word in the sentence in two different ways. Puns tend not to be funny, and often receives light sarcastic laughter. Many people fail at making these. One specific person comes into mind...
Chinese teacher: So, HOW is life?
Chinese student: Life is HAO.
Chinese teacher: *sighs* Why must I put up with this?
James: Oh, It's pun! *high fives*
Chinese student: wooooooooow...
Chinese teacher: Detention, both of you.