"Witty" and "facetious," along with "humorous," have to do with making people laugh or intending to make them laugh. We use the word "witty" for things that make us laugh because they are clever. The word "facetious" applies to attempts to make us laugh that don't quite succeed, sometimes because the remarks are made at the wrong time. "Humorous" is the broadest of these three, and it is used for almost anything that provokes good-natured laughter. Here's a funny fact about the word "facetious": it's one of the few English words that contain all the vowels (not including Y) in alphabetical order.