Short answers, pulled from the story.
Beat music is a British popular music genre that developed in Liverpool in the late 1950s and early 1960s, blending American rock and roll, rhythm and blues, skiffle, and traditional pop. It is also called British beat or Merseybeat, with the Mersey name taken from the River Mersey on whose estuary Liverpool sits.
Bill Harry, who founded the Liverpool music magazine Mersey Beat in 1961, claims to have coined the term based on a policeman's beat rather than a musical one. Bob Wooler, MC at the Cavern Club, separately renamed a band the Mersey Beats in February 1962, and by April that year they had become the Merseybeats.
Beat music used a strong backbeat common to rock and roll and R&B, often with a driving emphasis on all four beats of a 4/4 bar. Music writer Alan Clayson described it as "a changeless four-four offbeat on the snare drum," a style developed in the clubs of the St. Pauli neighbourhood in Hamburg, West Germany, where it was called the mach schau beat.
Liverpool's position as a major port gave it direct access to American records and guitars via sailors known as the Cunard Yanks, who brought back goods that were otherwise restricted by British trade rules. A combination of local solidarity, industrial decline, and a large Irish-origin population also contributed, and the city had an estimated 350 active bands by the late 1950s.
The Beatles' debut album Please Please Me, released in 1963, is most often cited as the record that best exemplifies the Merseybeat sound. Its release coincided with the mainstream rise of the genre in the United Kingdom and Europe.
Beat music was a direct influence on the American garage rock and folk rock movements of the 1960s, and shaped the development of psychedelic music. It also served as a source of inspiration for Britpop in the 1990s.