Short answers, pulled from the story.
The Summer of Love was a major social phenomenon centered in San Francisco's Haight-Ashbury district during the summer of 1967. As many as 100,000 mostly young people, including hippies, beatniks, and counterculture figures, converged on the neighborhood and Golden Gate Park. A PBS documentary called it "the largest migration of young people in the history of America."
The term originated with the Council for the Summer of Love, formed in the spring of 1967. The council included the Family Dog hippie commune, The Straight Theatre, The Diggers, the San Francisco Oracle, and about 25 other people who organized in response to the anticipated influx of young people into Haight-Ashbury.
The Human Be-In was a gathering of approximately 30,000 people in Golden Gate Park on the 14th of January, 1967, produced by artist Michael Bowen. Timothy Leary delivered his phrase "turn on, tune in, drop out" at the event, which helped shape the hippie counterculture and publicized hippie fashions ahead of the summer.
"San Francisco (Be Sure to Wear Flowers in Your Hair)," written by John Phillips of the Mamas and the Papas for his friend Scott McKenzie, became the era's anthem. Released on the 13th of May, 1967, the single reached number four on the US Billboard Hot 100 and number one in the United Kingdom and much of Europe, reportedly selling over seven million copies worldwide.
The Diggers were a radical anarchist group that had embedded in San Francisco in 1966. They ran a Free Store, published The Digger Papers with information on food, shelter, and human rights, and helped the council organize logistics for the summer crowds. The Haight Ashbury Free Clinics, which they supported, opened on the 7th of June, 1967.
A mock funeral called "The Death of the Hippie" was staged on the 6th of October, 1967. Organizer Mary Kasper explained that the event was meant to signal the end and tell people to "bring the revolution to where you live" rather than keep coming to Haight-Ashbury. By then, the neighborhood had experienced overcrowding, homelessness, hunger, drug problems, and crime.