In very basic terms, your identity can be described by giving your answer to the question: "Who am I?" In a rather similar way, your gender identity refers to a psychological sense or, or primary identification with, being either male or female. Developmentally, children learn what sex they are at a very early age. They usually develop a firm conviction (that is, a strong sense or belief) that they are either male or female at around age 2-3. This conviction generally becomes more stable and constant from about age 4. Although in most cases one's gender identity appears consistent with their biological sex, it is not necessarily an indication of one's gender role, sexual orientation, or range of sexual practices one may enjoy (which will become clear below).
For some people, however, the conviction that they are male or female may not match their assigned biological sex (e.g., the psychological sense that one is female despite being born in a male body). These individuals experience a strong and persistent cross-gender identification, which includes the desire to be, or the insistence that one is, of the opposite sex. In addition, these individuals experience persistent discomfort with their assigned biological sex and/or a sense that the gender role associated with their assigned biological sex is inappropriate. These individuals are commonly referred to as being transgender (which is in fact an umbrella term used to collectively refer to a variety of groups, individuals, and behaviours involving tendencies to vary from culturally conventional gender roles, such as transsexuals, cross-dressers, transvestites, drag queens, and other gender non-conformers etc). But here the term transsexual is arguably more appropriate for people with a cross-gender identification and should not be confused with other transgender concepts, such as cross-dressers, transvestites etc. Unfortunately these individuals continue to be ostracised, victimised, ridiculed and pathologised. Many transsexual people have a desire to transition, but the desire and degree of this transitioning may vary from person to person. A trans man refers to a female-to-male (FTM) individual, while a trans woman refers to a male-to-female (MTF) individual.