Short answers, pulled from the story.
Disco emerged in the late 1960s from the urban nightlife scenes of New York City and Philadelphia, particularly within African-American, Latino, Italian-American, and gay and lesbian communities. The discotheque concept was imported from France with the opening of Le Club at 416 East 55th Street in Manhattan on New Year's Eve 1960.
Disco declined sharply in the United States following Disco Demolition Night on the 12th of July, 1979, and continued falling in popularity through the early 1980s. The genre remained popular in Italy and parts of Europe throughout the decade and began spreading into India and the Middle East during the same period.
Notable disco DJs include David Mancuso of The Loft, Francis Grasso of The Sanctuary, Larry Levan of the Paradise Garage, Frankie Knuckles of the Chicago Warehouse, Nicky Siano of The Gallery, and Walter Gibbons. Levan and Knuckles were also prolific record producers; Knuckles went on to help develop house music in the 1980s.
Saturday Night Fever, released in December 1977 and starring John Travolta, became a massive commercial success whose soundtrack ranked among the best-selling albums of all time. Many music historians believe the film extended the disco era by several years, though critics argued it mainstreamed the genre in ways that distanced it from its African-American, Latino, and gay origins.
Discotheques provided a legally structured space for gay men and women at a time when New York state law prohibited homosexual behavior in public, including same-sex dancing. The Sanctuary in New York was described as the first totally uninhibited gay discotheque in America. At The Loft, David Mancuso's underground-but-legal parties allowed gay men to dance together without fear of police, at a time when many carried bail money when visiting gay bars.
Tom Moulton and his mastering engineer Jose Rodriguez developed the 12-inch single format after finding that standard 45 rpm singles could hold no more than five minutes of good-quality music. Pressing songs onto larger discs allowed for longer songs and remixes that could sustain the energy of a dancing crowd. The 12-inch single, also called the Maxi single, quickly became the standard format for disco DJs.