Gender

Gender is a social construct, and can differ from ones biological sex (transgender), and has values typically associated with it such as masculinity, femininity, androgyny, but some people don't express themselves with the attributes generally applied to their gender; for example a trans woman expressing themselves in a masculine manner is a tomboy, and they are valid.

Gender versus Sex
Sex is a biological value, generally determined by genitalia or chromosomes, for example a person with a penis is generally assigned male at birth, but biological attributes influenced by sex can differ, which is known as intersex.

Sex does not equal gender, and you can identify as a woman despite being biologically male, and that is perfectly okay.

How many genders?
Gender is a infinitely large spectrum, with many positions and identities, but the easiest way of looking at it is male and female, and everything in between being a term to describe your relationship with gender, for example demiboys being a term

to describe being both masculine and androgynous however, this model is still flawed as it forgets atrinary genders.

Resources

 * 1) https://apastyle.apa.org/style-grammar-guidelines/bias-free-language/gender