Bisexuality is a term that is applied to sexual behavior or orientation involving sexual or romantic attraction to both males and females. it is one of the three commonly used classifications of sexual orientation -- along with homosexual and heterosexual -- and is part of the continuum of sexual expression suggested by many theorists.
People often have distinct but not exclusive preferences for one sex over the other and may identify themselves as bisexual. Bisexuality has been observed and recorded in various human societies throughout most of human history, though the term itself was not used until the 19th century, along with heterosexuality and homosexuality.
Some people believe that bisexuals are individuals who are homosexual but not willing to admit the preference. it is sometimes pathologized when black men express it ("acting on the downlow") and associated with the reckless spreading of AIDS.