Your gender identity is how you feel inside and how you express those feelings. Clothing, appearance, and behaviors can all be ways to express your gender identity.
Most people feel that they’re either male or female. Some people feel like a masculine female, or a feminine male. Some people feel neither male nor female. These people may choose labels such as “genderqueer,” “gender variant,” or “gender fluid.” Your feelings about your gender identity begin as early as age 2 or 3.
Some people’s assigned sex and gender identity are pretty much the same, or in line with each other. These people are called cisgender. Other people feel that their assigned sex is of the other gender from their gender identity (i.e., assigned sex is female, but gender identity is male). These people are called transgender or trans. Not all transgender people share the same exact identity.
For more information on sexuality see: Sexual Orientation