A pun is, quite simply, a P.O.W.
If you did a double take just then, that's understandable. If you had a bit of a giggle, perhaps you've already gotten the joke. A pun is most certainly not a prisoner of war. It is, however, a play on words! Just like the above joking definition, puns take advantage of words and phrases that SOUND similar, but actually mean different things.
We come across puns constantly in common conversation and especially in comedy. Here are some examples:
I'd joke about chemistry with you, but I definitely wouldn't get a reaction.
I wasn't sure why the frisbee was growing larger and larger. Then it hit me!
The Easter Bunny isn't allowed to the North Pole anymore. He always eggs Santa on when the drinks start flowing.
The italicized words above all have multiple meanings. Reaction forms a pun because it could mean a laugh from the audience or a chemical event. Hit colloquially means that a realization occurred to someone suddenly, but in this case it literally means the frisbee striking his head. Eggs means to stimulate or push into doing something, but the word is also associated with the Easter Bunny's yearly job.
Many examples of puns may seem like real groaners, and those won't necessarily score you cool points at parties. That said, puns can also be incredibly insightful ways of linking formerly disconnected ideas, or even making sneaky social commentary. Stephen Colbert's 'The Word' segment on his popular comedy news show, The Colbert Report, is a great example.
