Although the word 'oder' does in fact mean 'or', there is a sneaky second meaning that often creeps up in spoken german. When thrown on the end of a sentence with a question mark, it turns the sentence in to a sort of question, confirming the statement just been said.
Heute ist Dienstag, oder? (It's Tuesday today, right?=)
Wir haben heute eine Prüfung, oder? (We have an exam today, right?)
In other words, 'oder?', with and only with the question mark, means 'right?'.
So beware when you see the word 'oder' with a question mark. Although, it's not hard once you get used to it...oder? :)
Absolutely agreed. I recently pointed this out in another recent discussion where Duolingo was using ", richtig?" in this sense, and I pointed out that it is more common to say ", oder?". In fact, as someone else pointed out, there are also other common ways of expressing this, such as "nicht wahr?", and then many regional variations, such as "gell?", "wa?", "nicht?", etc. I think Duolingo would do well to show some of these, especially "oder?" and "nicht wahr?".