Transgender means someone whose gender differs from the one they were assigned when they were born. Transgender people may identify as male or female or they may feel that none of the label fits them.
In order to express their chosen gender, transgender people may have a transition, or change from the gender they were assigned at birth. They may change their names, pronouns or style of dress. Some transgender people also choose a medical transition. That shows their depth of conviction towards their desire to change.