Lesbian: Someone who is female-identified and attracted romantically, erotically, and/or emotionally to other female-identified people.
Gay: Someone who is male-identified and attracted to other male-identified people in a romantic, erotic and/or emotional sense. Also used as an individual identity label for anyone who does not identify as heterosexual.
Bisexual: Someone who is attracted to both people of their own gender and another gender.
Queer: An umbrella term that includes anyone who a) wants to identify as queer and b) who feels somehow outside of the societal norms in regards to gender or sexuality. It is important to note that this is an in-group term and may be considered offensive to some.
Questioning: Someone who is in in the process of exploring and discovering their own sexual orientation, gender identity, or gender expression.
Intersex: A person whose combination of chromosomes, gonads, hormones, internal sex organs, gonads, and/or genitals differs from one of the two expected patterns.
Pansexual: sexual attraction, romantic love, or emotional attraction toward people of all sex or gender identities.
Polysexual: sexual attraction, romantic love, or emotional attraction toward people of multiple gender and sexual identities but not all.
Demisexual: A person who does not experience sexual attraction unless they form a strong emotional connection with someone. It's more commonly seen in but by no means confined to romantic relationships. The term demisexual comes from the orientation being "halfway between" sexual and asexual.
Definitions provided by the International Spectrum at the University of Michigan, UCLA LGBT Resource Center, and the AVEN Wiki