Short answers, pulled from the story.
Beatlemania was the intense fan frenzy surrounding the English rock band the Beatles, lasting from 1963 to 1966. The term was coined in October 1963 after the band's appearance on the UK variety show Sunday Night at the London Palladium, watched by 15 million viewers, and appeared in print in the Daily Mail on the 21st of October 1963.
Approximately 73 million viewers, about two-fifths of the American population, watched the Beatles' first live US television appearance on The Ed Sullivan Show on the 9th of February 1964. According to Nielsen ratings, it was the largest audience recorded for an American television program at the time. A second appearance on the 16th of February from the Deauville Hotel in Miami Beach drew another 70 million viewers.
The Beatles performed to an audience of over 55,000 at Shea Stadium in New York City on the 15th of August 1965, the largest of any concert they ever performed. The event set records for both attendance and revenue generation, with takings of $304,000. It was also the first time a large outdoor stadium had been used for such a purpose.
By 1966, the Beatles had grown frustrated with the restrictions of touring: they could not hear themselves play above the fans' screaming, were confined to hotel rooms, and faced escalating security threats including mob violence in the Philippines and death threats in Japan. Their final concert was on the 29th of August 1966 at Candlestick Park in San Francisco, after which they became a studio-only band. Ringo Starr later said they gave up at the right time, since "Four years of Beatlemania was enough for anyone."
A 1966 study published in the British Journal of Clinical Psychology found that Beatles fans were not unusually neurotic, describing Beatlemania as "the passing reaction of predominantly young adolescent females to group pressures of such a kind that meet their special emotional needs." A 1997 study later recognised Beatlemania as an early demonstration of proto-feminist girl power, and authors Barbara Ehrenreich, Elizabeth Hess and Gloria Jacobs argued in their 1986 book that it was "the first mass outburst of the '60s to feature women."
A crowd of 300,000 people, roughly half the population of Adelaide, welcomed the Beatles on the 12th of June 1964 during their world tour. It was the largest recorded gathering of Australians in one place and twice the number of people who had greeted Queen Elizabeth II on her royal visit to Australia in 1963.