Different cultures across time and around the world have conceptualized gender identity, gender expression differently. Currently transgender is a broad term that refers to people who experience their gender identity or express their gender in ways that do not conform to their assigned sex at birth.

Transgender identity includes many overlapping categories.Transsexuals are transgender people who live or wish to live full time as members of the gender opposite to their birth sex. Biological females who wish to live and be recognized as men are called female-to-male (FTM) transsexuals or transsexual men. Biological males who wish to live and be recognized as women are called male-to-female (MTF) transsexuals or transsexual women. Transsexuals usually seek medical interventions, such as hormones and surgery, to make their bodies as congruent as possible with their preferred gender.

The process of transitioning from one gender to the other is called sex reassignment or gender reassignment.Cross-dressers or transvestites comprise the most numerous transgender group. Cross-dressers wear the clothing of the other sex. They vary in how completely they dress (from one article of clothing to fully cross-dressing) as well as in their motives for doing so. Some cross-dress to express cross-gender feelings or identities; others crossdress for fun, for emotional comfort, or for sexual arousal. The great majority of cross-dressers are biological males, most of whom are sexually attracted to women.Drag queens and drag kings are, respectively, biological males and females who present part-time as members of the other sex primarily to perform or entertain.

Their performances may include singing, lip-syncing, or dancing.  Drag performers may or may not identify as transgender. Many drag queens and kings identify as gay, lesbian, or bisexual.Other categories of transgender people include androgynous, bigendered, and gender queer people.