I have decided to include this category for two reasons. The first reason is because when some people hear the terms "transgender/sexual", "genderqueer", or "bi-gendered" they think that this means the person is intersexed, which usually isn't true. The second reason is that intersexed people are discriminated against and often forced to conform to society's rules on gender roles.
To be intersexed, a person must have been born with atypical reproductive or sexual anatomy. As you can imagine, this can take several forms. A person who is, by all outward signs, male may have ovaries instead of testes. A person who looks female may have an elongated and thickened clitoris with a blocked vaginal opening. A man might have a uterus inside his abdomen, or have a split scrotum. Intersex may also be as "simple" as having a mixture of XX and XY chromosomes without having any outward appearance.
It used to be very common for doctors to decide whether an intersexed baby was a "boy" or a "girl". Upon deciding, the child was subjected to surgery and sometimes hormones to "normalise" the genitals so they would look like a "proper" boy or girl. This practise is less common now than it was 30 years ago, but it is still quite prevalent.
Again, intersex does not equal transgender or transsexual. Intersex has to do with the body and how it developed in the womb, while transgender/transsexual is more to do with how a person feels internally about their gender.