The following definitions will help you to understand and properly use some of the terms associated with sexual orientation and gender identity.
Biological Sex: This can be considered our "packaging" and is determined by our chromosomes (XX for females; XY for males); our hormones (estrogen/progesterone for females, testosterone for males); and our internal and external genitalia (vulva, clitoris, vagina for females, penis and testicles for males). About 1.7% of the population can be defined as intersexual--born with biological aspects of both sexes to varying degrees. So, in actuality, there are more than two sexes.
Gender Identity: Our innermost concept of self as "male" or "female"--what we perceive and call ourselves. Individuals are conscious of this between the ages of 18 months and 3 years. Most people develop a gender identity that matches their biological sex. For some, however, their gender identity is different from their biological sex. We sometimes call these people transsexuals, some of whom hormonally and/or surgically change their sex to more fully match their gender identity.
Gender Role: This is the set of roles and behaviors assigned to females and males by society. Our culture recognizes two basic gender roles: masculine (having the qualities attributed to males) and feminine (having the qualities attributed to females). People who step out of their socially assigned gender roles are sometimes referred to as transgender. Though transgender has increasingly become an umbrella term referring to people who cross gender/sex barriers, many people find any umbrella term problematic because it reduces different identities into one oversimplified category.
Transgender: Refers to those whose gender expression at least sometimes runs contrary to what others in the same culture would normally expect. Transgender is a broad term that includes transsexuals, cross-dressers, drag queens/kings, and people who do not identify as either of the two sexes as currently defined. When referring to transgender people, use the pronoun they have designated as appropriate, or the one that is consistent with their presentation of themselves.
Transsexuals are individuals who do not identify with their birth-assigned genders and sometimes alter their bodies surgically and/or hormonally. The Transition (formerly called "sex change") is a complicated, multi-step process that may take years and may include, but is not limited to, Sex Reassignment Surgery.
Gender Expression: Refers to the ways in which people externally communicate their gender identity to others through behavior, clothing, haircut, voice, and emphasizing, de-emphasizing, or changing their bodies' characteristics. Typically, transgender people seek to make their gender expression match their gender identity, rather than their birth-assigned sex. Gender expression is not necessarily an indication of sexual orientation.
Sexual Orientation: This is determined by our sexual and emotional attractions. Categories of sexual orientation include homosexuals--gay, lesbian--attracted to some members of the same sex; bisexuals, attracted to some members of more than one sex; and heterosexuals, attracted to some members of another sex. Orientation is influenced by a variety of factors, including genetics and hormones, as well as unknown environmental factors. Though the origins of sexuality are not completely understood, it is generally believed to be established before the age of five.
Sexual Identity: This is how we perceive and what we call ourselves. Such labels include "lesbian," "gay," "bisexual," "bi," "queer," "questioning," "heterosexual," "straight," and others. Sexual Identity evolves through a developmental process that varies depending on the individual. Our sexual behavior and how we define ourselves (identity) can be chosen. Though some people claim their sexual orientation is also a choice, for others this does not seem to be the case.
Coming Out (of the closet): To be "in the closet" means to hide one's identity. Many LGBT people are "out" in some situations and "closeted" in others. To "come out" is to publicly declare one's identity, sometimes to one person in conversation, sometimes to a group or in a public setting. Coming Out is a life-long process--in each new situation a person must decide whether or not to come out. Coming out can be difficult for some because reactions vary from complete acceptance and support to disapproval, rejection and violence.
Queer: Historically a negative term used against people perceived to be LGBT, "queer" has more recently been reclaimed by some people as a positive term describing all those who do not conform to rigid notions of gender and sexuality. Queer is often used in a political context and in academic settings to challenge traditional ideas about identity ("queer theory").
Questioning: Refers to people who are uncertain as to their sexual orientation or gender identity. They are often seeking information and support during this stage of their identity development.
Ally: Any non-LGBTQ person who supports and stands up for the rights of LGBTQ people.
Homophobia: Refers to a fear or hatred of homosexuality, especially in others, but also in oneself (internalized homophobia).
Heterosexism: Bias against non-heterosexuals based on a belief in the superiority of heterosexuality. Heterosexism does not imply the same fear and hatred as homophobia. It can describe seemingly innocent statements, such as "She'd drive any man wild" based on the assumption that heterosexuality is the norm.
Transphobia: Fear or hatred of transgender people; transphobia is manifested in a number of ways, including violence, harassment, and discrimination.
Adapted from GLSEN: Talking the Talk
Some definitions adapted from:
Warren J. Blumenfeld, co-author Looking at Gay and Lesbian Life and ed.
Homophobia: How We All Pay the Price