Let's start with the basics. Gender and sex are two different things. They are related, but they DO NOT mean the same thing. This confuses some people, but we promise, it's not that confusing.
Sex is how organisms (i.e. PEOPLE) are classified based on their reproductive organs and functions. Simply put, sex is based on BIOLOGY--whether someone has ovaries or a penis. Sex is what makes an individual MALE or FEMALE.
Gender classifies people by behavioral, cultural or psychological traits. Simply put, Gender is based on CULTURE (culture being made up of your practices, beliefs and objects or possessions). Gender is what makes an individual MASCULINE or FEMININE.
To understand how gender and sex are connected, here's a little analogy:
Think about a coat rack. Sex is the physical structure of the coat rack. Gender is what you hang on the coat rack--it's the coats and hats and maybe that weird poncho your mom makes you wear in the rain.
Need something more concrete? Here's an example: Let's say you're female. You have ovaries, a vagina and all other girl parts. This is your sex. Consider this your coat rack.
Now moving on to what you put on the coat rack. This is a little trickier because gender is more complex. Let's say you like to cheerlead and the color pink. You wear your hair long and have been known to cry in public. These would be the coats and hats that make up your gender and hang on the coat rack. From this, we would assume your gender is feminine.
However, sometimes it's not that clear cut. Your gender may not always be the same as your assigned sex. And that's okay...