Bisexual is someone who is attracted to both genders, be it a man or a woman. A pansexual is a person who is sexually, romantically or emotionally attracted towards people regardless of their sex or gender...

Gay is an umbrella term, which covers any person who is a homosexual, regardless of gender. Lesbian is specifically used to refer to women who are attracted to other women.

Gay is a term commonly used to refer to homosexuals. The term 'homosexual' was first used by Victorian scientists who regarded same-sex attraction and sexual behavior as symptoms of mental disorders...