Please don't take this offensively, I'm trying to learn. Could you please explain to me the different between women and men? Because besides of physically I can't see the difference and that's why when people ask me my gender I don't know what to answer. Non-binary, female... I always say yes. Because in the 21st century we're breaking the steorotypes surrounding women and men so these don't define them. So what's the difference?
Your question more or less boils down to “What is gender?”, which is sort-of impossible to answer. The kind of direct, empirical difference between different genders that you’re looking for doesn’t exist, so it must be that gender isn’t a thing; but at the same time, many people have an innate, intuitive sense of their own gender. What’s going on here?
Some statements about the world are true, like “High pitch sounds have a shorter wavelength than low pitch sounds” or “I like hot chocolate”, and some statements about the world are false, like “Everyone is a native speaker of English” or “I like coffee”. Sometimes, especially for statements about yourself, you can get a sort-of “truth value feeling” out of a statement. “I like hot chocolate” feels innately true to me in a way that “I like coffee” doesn’t.
Gender can be the same way. Part of why I know I’m nonbinary is that “I’m nonbinary” feels right and “I’m a girl” and “I’m a boy” feel wrong in some way. I’m not thinking in terms of stereotypes or behavior or clothing or presentation or anything else, just in terms of what feels right. Gender is socially constructed and thus heavily informed by dated stereotypes and traditions like “boys don’t wear dresses”, but that doesn’t mean it doesn’t exist. People are the gender they are because they feel that way, because they feel like they are that gender.
If that didn’t make sense to you and/or you don’t have an internal, innate sense of gender, you might be agender. If you find the label helpful, you can go ahead and start using it, but if you don’t want to for any reason that’s okay too. And if you’re not sure if it’s right for you, you can always try it on for a bit and see how it feels.
Hope that helps, as always feel free to ask for clarification/any follow up questions.