Intersex is when someone is born with both boy and girl parts, or parts that are not clearly male or female. Like if you had a toy that was half car and half airplane, that would be like intersex.
Sometimes, doctors do surgery to try to make the intersex person look more like a boy or girl on the outside, but this can be really hard for the person, and some people think it's wrong.
It's important to remember that there is nothing wrong with being intersex or having parts that are not easily labeled as male or female. Everyone is unique and special in their own way, and that's what makes the world a fun and interesting place!