What is the difference between ou and où in French?

où means where, ou means or

I just wanted to add that, in this case but not always, both Words are pronounced exactly the same. Sometimes in French an accent is added just to distinguish that it is a different Word.

Other examples: a - third person present from verb avoir

à- to, at, in + a lot of other things

jeune - adj. for young

jeûne - fasting

If you would like more examples you can look up French homographs online. (: