Transsexualism is when an individual identifies with a gender inconsistent or not culturally associated with their assigned sex, i.e. in which a person's assigned sex at birth conflicts with their psychological gender. A medical diagnosis can be made if a person experiences discomfort as a result of a desire to be a member of the opposite gender, or if a person experiences impaired functioning or distress as a result of that gender identification.
Transsexualism is stigmatized in many parts of the world, but it has become more widely known in Western culture since the mid to late 20th century, concurrently with the sexual revolution and the development of sex reassignment surgery (SRS).
There are cultures that have no difficulty integrating people who change gender roles, often holding them with high regard. Some maintain that transsexuals uphold the traditional role of what were called "Two-Spirit" people found among certain Native American tribes.
First of all, the word is spelled 'transsexual', and it is an adjective that describes a person who suffers from a natural, congenital birth condition known as Transsexualism.
Second, we all either have a male gender identity, or a female gender identity, and this identity is permanently set in the womb by a hormonal wash of androgens on the developing fetal brain around the 12th-14th week of pregnancy. What your body looks like, how people treat you, how you choose to express yourself, how society expects you to be, are all irrelevant to your internal gender identity.
A transsexual person is either a person born with a male brain and a female anatomy, or a female brain and a male anatomy. Because the brain cannot be changed (nor would we want to change it) the only way to treat Transsexualism is to correct the body as much as we can using surgery and hormonal replacement therapy so it matches the brain. This process is known as Gender Transition. Depending on the individual, their response to hormones, their access to surgery, and their willingness to do the work necessary to overcome the condition itself, Transsexualism can, for all practical purposes, be completely corrected via Transition so that it does not negatively affect a person's life. Once corrected, most people who were born suffering from Transsexualism blend back into society as their identified gender, and live relatively normal lives. The few who do not usually fall into one of three categories.
1. Activists/Advocates - These are people who have chosen to let the world know they were born Transsexual, and dedicate themselves to educating the public, petitioning for anti-discrimination laws, assisting other transpeople in Transitioning, and so on. The trade-off for performing this important public service is that these people end up adopting the identity of "transsexuals" in the eyes of the media and general public.
2. Transsexuals - some people choose to allow Transsexualism to supersede their own identity, and willingly let society label them "Transsexuals." Most of the time, these are older transwomen who are either unable to pass convincingly (unfortunate), or unwilling to do the work required to pass convincingly (pitiful.) Transmen rarely identify as "Transsexuals" because virtually all Transmen are able to pass after Testosterone Therapy. As it stands today, with available therapies, there really is no reason why anyone need be labeled a "Transsexual" unless they desire it.
3. Sex workers - these people are not suffering from Transsexualism in the true sense because they rarely seek to Transition fully. Most are gay men who've feminized their bodies with hormones, and gotten breast implants and other cosmetic surgeries in order to appear female for the purpose of performing in pornographic films, or engaging in prostitution. The majority keep their male genitals intact, and use them in the course of their chosen work, something most Transsexual women would find abhorrent. Unfortunately, this image was representative of the typical Transsexual person for many years. In the last decade, this has finally started to change, although many people still offensively refer to Transsexual women as "shemales", "trannies", "chicks with d*cks" and so on.
Last, beware of anyone who tries to convince you that Transsexualism isn't a medical condition, or that there is some virtue in calling oneself "a transsexual", or worse, embracing this condition as a desirable identity. People who advocate we take pride in a correctable medical condition like Transsexualism are ludicrous, and their thinking is hypocritical, since ostensibly a person who is proud of being born like this would not seek to change themselves in any way. Transsexualism is a tragic, life-robbing condition that causes tremendous misery, pain and often death, in those who suffer from it. The gender dysphoria caused by Transsexualism can overshadow everything in a person's life, often for decades. It destroys families, marriages, costs people their friends, and often everything else they have as well. Like a tornado, it leaves a wake of destruction behind, so the sooner a person can address it, and put it behind them, the better. Fortunately, now that the public and the medical community are being educated properly, Transsexualism is being diagnosed and treated at younger ages, so passing becomes far less of an obstacle to a successful Transition.
Hopefully one day, perhaps with some form of stem-cell therapy, doctors will be able to reverse Transsexualism in utero, or prevent it from happening in the first place.