In this website, gender identity means:
someone's conception of her/his own gender,
which may or may not be the same as the gender she/he was assigned at birth.
Although most people feel comfortable with living in a male or in a female body such as they have since their birth, some are not.
These people are called "trans" people.
Some of them are even so uncomfortable with the physical sex of their body
that they want to have it changed,
either by hormonal or by surgical procedures - or both.
Some people define "post-operative" trans people not as trans people,
but in this website the term trans or transgender is also used to include this group.