People outside the trans experience have a truly hard time understanding the magnitude of the task of changing gender expression. No one would ever do this unless they were forced to by their own psychology. We must all, at the very least, understand that, "Transgender" is a term used to describe people whose gender identity differs from the sex they were assigned at birth. Gender identity is a person's internal, personal sense of being a man or a woman (or boy or girl.) For some people, their gender identity does not fit neatly into those two choices. For transgender people, the sex they were assigned at birth and their own internal gender identity do not match.
Okay, now that we got that out of the way... We also need to know that trying to change a person's gender identity is no more successful than trying to change a person's sexual orientation -- it doesn't work. So most transgender people seek to bring their bodies into alignment with their gender identity. This is called transition. As part of the transition process, many transgender people are prescribed hormones by their doctors to change their bodies. Some undergo surgeries as well. But not all transgender people can or will take those steps, and it's important to know that being transgender is not dependent upon medical procedures. The realization that you're in the wrong gender or perhaps have been categorized in the wrong sexuality- can come at any age.