Someone explain what is gender, sex and why romance and sex in together in sexuality

Sex is what I had with yo mama last night   3 reply

Gender is what you identify with, for example man, woman, non binary, etc. Sex is the gender you're assigned with at birth (W, M). I didn't understand the last part of this tho   reply

K. I can't make it short, cuz there's a lotta differences that some people tend to mess up with. I'll just explain in points to make it look as neat as possible. G͟e͟n͟d͟e͟r͟: Basically what you internally FEEL you are. It's your inner identity. Eg.- Cisgender, bigender, gendefluid, non-binary, etc. S͟e͟x͟: Basically what you PHYSICALLY ......   reply

Sex isn’t real, gender is a performance and sexuality is expansive.   reply