Gender is something that many people take for granted. Their bodies match their minds (cisgender), and so it has become acceptable to define gender as the body parts you are born with and, secondarily, the way you present yourself. However, this is a narrow view and ignores the fact that there are a great number of people who do not fall within the gender binary of male and female (genderqueer). More specifically, it ignores those who feel discordance between their body and their mind (transgender), people born with atypical physical features (intersex), and those who feel no gender (agender), switch between genders (genderfluid) or feel both male and female (bigender). Gender is best defined by how one identifies in their mind, not by morphology. It exists on a spectrum, and is not constrained by sexuality.
Yee Won Chong shares a story, Beyond the Gender Binary, about the challenges of navigating the world while transgender, and provides suggestions on being a good ally. He converts practical skills and experiences and is currently Development Director at Western States Center, a regional non-profit that trains people to organize toward a just, equitable and democratic society.
What follows are links to more information about different named parts of the gender spectrum, as well as concepts and terms relevant to gender
This is also a great link for sharing positive perspectives about trans* people from around the world.