Gender dysphoria used to be called “gender identity disorder.” But the mismatch between body and internal sense of gender is not a mental illness. Instead, what need to be addressed are the stress, anxiety, and depression go along with it.
The condition has also been called “transsexualism.” But this term is outdated. Some consider it offensive. Now "transgender” is often used to describe someone who feels his or her body and gender do not match.
Gender nonconforming (GNC) is a broader term that can include people with gender dysphoria. But it can also describe people who feel that they are neither only male or only female. Informally, people who identify with both genders or with neither gender might call themselves "genderqueer."
Gender dysphoria is not homosexuality. Your internal sense of your gender is not the same as your sexual orientation