A pun is a form of wordplay that exploits the multiple meanings of a word or the fact that there are words that sound alike but have different meanings.
Here are some examples:
* "I'm reading a book about anti-gravity. It's impossible to put down!" This pun uses the word "put down" to mean both "stop reading" and "place on a surface".
* "Time flies like an arrow. Fruit flies like a banana." This pun plays on the similar sounds of "flies" in the context of time and insects.
* "I used to be a banker, but I lost interest." This pun plays on the word "interest" as both a feeling and a financial concept.
Puns can be humorous, clever, or even groan-worthy, but they always rely on the multiple meanings of words or words that sound alike.