Understanding the difference between Gender and Sex could be one of the most important steps to understanding what it means to be transgender or genderqueer. The basic idea is that gender refers to your identity—the mental/psychological aspect—while sex is your physical, biological, or legal classification. For most people, the difference is moot because their gender identity matches their assigned sex, and this can make it harder to understand that they are two different concepts. For people who are transgender, however, their gender identity does not match their biological sex. The opposite of this is cisgender, where someone's gender and sex are the same.
According to the World Health Organization , gender is also considered a social construct consisting of roles, behaviours, and other attributes that are considered "appropriate" for males or females. Because of this, gender can vary greatly from culture to culture. In the west, gender is generally seen as a binary based on sex, but with increased awareness of transgender or genderqueer people, the binary is slowly being replaced by the concept of a gender spectrum. Some other cultures already have multiple genders; Two-Spirit people are examples of a third gender in many Native American societies, as well as Hijra in India.