Short answers, pulled from the story.
The Three Tenors were Italian tenor Luciano Pavarotti and Spanish tenors Plácido Domingo and José Carreras. They first performed together at the Baths of Caracalla in Rome, Italy, on the 7th of July 1990, the eve of the 1990 FIFA World Cup final.
Carreras Domingo Pavarotti in Concert, recorded at the Baths of Caracalla in 1990 and released by Decca, holds the Guinness World Record for the best-selling classical music album. It reached number one in Italy, Spain, Australia, the Netherlands, and the United States.
The first concert was organized to raise money for the José Carreras International Leukemia Foundation and to welcome Carreras back to opera after his successful treatment for leukemia. His friends Domingo and Pavarotti participated, and producers Mario Dradi, Elmar Kruse, and Herbert Chappell conceived the event.
On their first worldwide tour, each tenor received around one million dollars per concert, a fee without precedent for classical musicians at the time.
The U.S. Federal Trade Commission brought antitrust action against Warner Bros. and Vivendi Universal for conspiring not to advertise or discount the Rome and Los Angeles concert albums to protect sales of the jointly released Paris album. Separately, two of the three tenors paid an undisclosed fine to the German government as part of an out-of-court settlement for tax evasion; their promoter Matthias Hoffmann was sentenced to jail.
For the 1990 Rome concert, the tenors accepted small flat fees and donated them to charity, but the album reaped millions in profits for Decca, leaving the tenors with no royalty payments. Years later, Pavarotti's former agent Herbert Breslin wrote that Pavarotti had secretly received 1.5 million dollars from Decca, which Domingo and Carreras - not contracted to Decca - did not receive.