Sex refers to the biological and physical differences between male and female organisms. In humans, this includes factors like reproductive organs and chromosomes. Typically, males have XY chromosomes, and females have XX chromosomes.
It's important to understand that while sex is about biology, it also relates to how people identify themselves. Some people might identify as male or female, while others may see themselves differently.
As you grow, you will learn more about the differences between genders and how they impact people's lives and identities. For now, it's good to know that 'sex' can refer to both biological differences and the way people understand themselves in the world.