Taking into consideration there are more than 7 billion people who are alive on this planet, it is good to understand that there are some people who are not female or male. Some of these people, they may not even be aware of the type of their sex. Sometimes, people assume that only people of XX and XY are around.
Sex is normally biological concept. Someone can be female or male. However, gender is a social construct, a woman or a man. Sex is not something that was invented by the human being since nature found it a long time ago.
For human being, sex is genetic concept and at least 99 percent of people have well recognized sex. Male have XY genotype and they do exhibit sexual characteristics known to men such as body hair and beards. Their action has to be done in the behavior range of the males. They can identify themselves like men, the female can have the xx genotype, and they do exhibit characteristics of females such as breasts. They also have the same self identification and behavior. However, around 1 percent of people are not found in any of these criteria.
The intersex condition
These are children who were born having ambiguous genitalia. They can have XY or XX genotype. As they grow up, the bodies will develop as intermediate pattern or along female and male pattern. They can decide to behave like females or males. It is hard to tell what it is happening when the child is growing up since the sex chromosomes cannot do everything when it comes to determine how the child developed while in a womb. At the beginning, a fetus is found in a default form and he can develop as a female or a male. As the time passes, the hormones developed can feminize or masculinize the brain and the body of a fetus. This is a process known as sex differentiation. When this goes wrong, the baby can be born without fitting well in the female or male body.
Some humans do not have the XY or XX genes. Some can be XXY, XXYY, X and XXX.
True hermaphroditism: these are people who have testicular and ovarian tissues at the same time. Some people can have feminine body and breast and they can menstruate. However, the labia can be fused partly and this forms an incomplete scrotum. However, most hermaphrodites have masculine physique compared to feminine.
The transsexuals are known as trans-gendered people. They are people who have the brain, which failed to feminize or to masculinize fully at birth, but the bodies did. Since the mind cannot be changed, then doctors try to change the bodies. This can be done with some success. However, it is not easy to know if someone was born with this problem with medical examination.
These are people who have different sets for their genes, the head may have genes of a certain person while the ovaries may show that it is for someone else.