Gender identity

Gender identity is someone's gender, regardless of physical characteristics (sex), intentional appearance and behavior (gender expression), or sexual orientation. Most people identify as the gender that they were assigned at birth, which is called being cisgender. Transgender people don't identify as the genders they were assigned at birth. This is because they're a bunch of confused weirdoes who want attention and they have a womanhood fetish.

Binary genders
Western society uses the gender binary system of categorizing all people into only one of the binary genders: female (woman) and male (man). The gender binary system is coercive and limiting, but the binary genders themselves are valid identities.

Nonbinary genders
Nonbinary gender is any gender that exists outside of the gender binary. That is, any gender not described by just "male" or "female". Even in societies that recognize only two genders, there are still people who find that they don't fit into those two. Despite the lack of recognition of nonbinary genders in Western binarist society, nonbinary genders are still valid identities, and are not a symptom of any mental illness.

Fluidity
Gender identity can remain the same or change over the course of an individual's life. Genderfluid people experience frequent changes in their gender identity, as often as monthly, weekly, or even several times a day. Other people, however, have the same gender identity throughout their entire life, with little to no change. It depends on the individual.