Short answers, pulled from the story.
Karl Maria Kertbeny coined the term heterosexual, alongside the word homosexual, in 1869. The abstract noun heterosexuality is first recorded in 1900, and the term did not enter common use until the 1960s.
Heterosexuality is romantic attraction, sexual attraction, or sexual behavior between people of the opposite sex or gender. As a sexual orientation it is an enduring pattern of emotional, romantic, or sexual attraction to people of the opposite sex, and someone who is heterosexual is commonly called straight.
Major studies report that between 89% and 98% of people have had only heterosexual contact within their lifetime. An October 2012 Gallup poll found 96.6% of U.S. adults identified as heterosexual, with a margin of error of plus or minus one percent.
Scientists do not know the exact cause but theorize a complex interplay of genetic, hormonal, and environmental influences, and do not view it as a choice. They favor biological theories, as there is more evidence for nonsocial, biological causes than social ones, especially for males.
Straight began as a mid-20th century gay slang term for heterosexuals, drawn from the phrase to go straight, as in the straight and narrow, meaning to stop engaging in homosexual sex. One of the first such uses came from author G. W. Henry in 1941.
Heteronormativity is a world view that promotes heterosexuality as the normal or preferred sexual orientation and can assign strict gender roles to males and females. The term was popularized by Michael Warner in 1991.
Sexual orientation is stable and unlikely to change for the vast majority of people, though some research shows change does occur and is more likely for women than men. A 2012 study of 2,560 adults found 2% reported a change in sexual orientation identity over a 10-year period.