Sometimes, I read that "quae" could be used, not only as a relative word, but also as an interrogative word.

Sometimes I read that it's not like that in the correct usage.

Quote, from a fellow Latin learner, more advanced than me: 

"***In practice***, it seems that "quis" is right for masculine and feminine."

So, what are the rules, and if it's correct why some people think it's not, and vice-versa, if it's not correct?

@Answer Thank you for the declension table, but I know that "quis" and "quae" are question-words (as stated in my question), I just want to know why several people, more advanced in Latin, tell us to use "quis" for masculine and feminine (because it's the right use, "in practice" = the natural use, meaning: it's like this that Romans spoke.)

And why for masculine and feminine if it can be declined in masculine/feminine?

Why "Quis est femina?" and not "Quae est femina?"

My course teach me "Quis" for every gender and doesn't accept "Quae". 

My question is about "correct usage".

If this course teach that, if I read and heard so many people telling to use "Quis" with both gender and not "Quae" what could be the reason if the use is right?