From the point of view of English language, when is the answer to a question "obvious", in general?

I am pondering over this question for a while. I was having a discussion with a friend and when she asked me a question, I responded to her that "Isn’t it pretty obvious?" and she responded to me that the answer to the question wasn’t obvious to her. Now, this is the definition of the word, obvious, according to Cambridge online dictionary: easy to see, recognize, or understand.

So, in English, when is it okay to state or use the word "obvious"? When is the answer to a question obvious and when is it not?