binary genders is similar to actual binary, where it has to be either 1 or 0 (only two states); it's the idea that there is only two genders that you can be, which is what the majority of people believe and what society uses. thinking you're outside of this binary system is being non-binary.
gender fluid is supposedly about being able to change your mind gender back and forth; new concept and you'll likely end up in the mental asylum if you seriously believe in it.