People who have gender dysphoria feel strongly that they are not the gender they physically appear to be.
For example, a person who has a penis and all other physical traits of a male might feel instead that he is actually a female. That person would have an intense desire to have a female body and to be accepted by others as a female. Or, someone with the physical characteristics of a female would feel her true identity is male.
Avoidant personality disorder is characterized by feelings of extreme social inhibition, inadequacy, and sensitivity to negative criticism and rejection. Yet the symptoms involve more than simply being shy or socially awkward. Avoidant personality disorder causes significant problems that affect the ability to interact with others and maintain relationships in day-to-day life. About 1% of the general population has avoidant personality disorder.
Feeling that your body does not reflect your true gender can cause severe distress, anxiety, and depression. "Dysphoria" is a feeling of dissatisfaction, anxiety, and restlessness. With gender dysphoria, the discomfort with your male or female body can be so intense that it can interfere with the way you function in normal life, for instance at school or work or during social activities.
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 that 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 But this term is outdated.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.