Alternative names:
pseudohermaphroditism; hermaphrodite; intersexual

Accepted definition: A person born with both male and female sex organs. This is a vague, confusing and inaccurate definition. There are 3 labels of Hermaphrodites: True, Male pseudo and Female Pseudo. All are equally genuine. Intersexual - A term referring to being of both sexes.

TRUE
A person born with both ovary and testicular tissue, this could be 2 separate gonads ( one of each) or a combination of both in one (an ovotestes). The genitalia can vary from completely male or female, to a combination of both or even ambiguous looking. The chromosome (karotype) compliment can be XX (female), XY (male), XX/XY (mosaic) or even XO (extremely rare). Those XX with female genitalia are raised female ( some have even given birth). Those XY with male genitalia are raised male ( a few have fathered children). The children born XX/XY or XO (with genitalia male or female are raised in the sex they look most like) ,Those born with ambiguous genitalia have many medical tests for the doctors to determine which sex they should be assigned. Doctors then recommend early surgery to make the child look physically like the sex assigned to them.

CAUSES
The causes are not known, The medical community does know this is a very rare condition but do not have accurate figures to how many people have this condition (depending on the literature between 350-450 known cases).

FEMALE PSEUDO
A person born XX with normal female internal organs but with "masculanized" genitalia. They can appear more male then female or a combination of each.

CAUSES
The most common is Congenital Adrenal Hyperplasia (CAH) it occurs approximately 1:14,000 births. This is when the adrenal glands overproduce testosterone. 

MALE PSEUDO
A person born XY with testes. The external genitalia are usually female but can be ambiguous.  Read the complete study here