Short answers, pulled from the story.
Many historians point to Jackie Brenston and his Delta Cats recording Rocket 88 in March 1951 as the pivotal moment. This track was produced by Sam Phillips at Sun Studio and featured a distorted guitar sound caused by a broken amplifier. Ike Turner later clarified that Rocket 88 was rhythm and blues yet acknowledged it as the cause of rock and roll existing.
Alan Freed, a disc jockey in Cleveland, Ohio, began playing this music style in 1951 and referred to it as rock and roll on his mainstream radio program. He found the term on the record Sixty Minute Man by Billy Ward and his Dominoes and used it to describe swing with a modern name. Freed became internationally known for promoting African-American rhythm and blues music on the radio in the United States and Europe under the name of rock and roll.
Elvis Presley recorded the regional hit That's All Right at Sam Phillips' Sun Studio in Memphis in July 1954. By 1956, he had emerged as the singing sensation of the nation and popularized rock and roll on a wider scale than any other single performer. His style combined with black influences created controversy during a turbulent time in history.
The retirement of Little Richard to become a preacher in October 1957, the departure of Presley for service in the United States Army in March 1958, and the scandal surrounding Jerry Lee Lewis' marriage to his thirteen-year-old cousin in May 1958 gave a sense that the initial phase of rock and roll had come to an end. The deaths of Buddy Holly, the Big Bopper and Ritchie Valens in a plane crash in February 1959 and the breaking of the Payola scandal in November 1959 further contributed to this perception.
Rock and roll appeared at a time when racial tensions in the United States were entering a new phase with the U.S. Supreme Court ruling that abolished the policy of separate but equal in 1954. The crossover of African-American race music to a growing white youth audience involved both black performers reaching a white audience and white musicians performing African-American music. Some people believe that the music had a positive influence on the civil rights movement because of its widespread appeal to both Black American and White American teenagers.
The Beatles, initially known as the Quarrymen, produced a form of rock and roll revivalism that carried them and many other groups to national success from about 1963 and to international success from 1964. This movement was known in America as the British Invasion and included groups from British cities like Liverpool, Manchester, Birmingham, and London. The Beatles were particularly influenced by later rockabilly acts like Buddy Holly.