Gender = psychological Sex = physiological/biological Sexual orientation = the sex(es) or gender(s) some is attracted to. Gender is fluid and more of an identifying choice while sex is what you're born with. Some people chemically, emotionally, and mentally don't match their sex so they identify as what they fit (which is obviously fine). The way chemicals act in their bodied may affect who they are (i.e. a male born in a female's body, a female born is a male's, etc.) and many times they grow up very confused. Some people simply choose to identify as something other than their sex while some people feel they don't even have a gender. There are also people who are born with a rare sex or a mix of some sort who don't just identify by that because that isn't all they are; they too choose whichever gender suits them the best. In the end, it's all fine.