Short answers, pulled from the story.
President Nixon left the White House on the 17th of February 1972 and arrived in Shanghai at 7 am on the 21st of February 1972. This journey marked the first time a U.S. president had visited mainland China while in office.
Henry Kissinger secretly visited Beijing in July 1971 during a trip to Pakistan to lay the groundwork for the upcoming visit. Transcripts from White House meetings show Nixon began working to open communication channels from his first day in office.
Almost as soon as the American president arrived in the Chinese capital, CCP Chairman Mao Zedong beckoned him for a quick meeting despite being hospitalized for several weeks up to only nine days before Nixon's arrival. They discussed political differences with Mao joking that he voted for Nixon during his last election.
The United States wanted to gain leverage over the Soviet Union and resolve the Vietnam War by flexibly dealing with both countries. National Security Council staffer Winston Lord noted that the U.S. sought to pressure them to reduce support for North Vietnam through this strategic shift.
Nixon stated that building a bridge across 16,000 miles and 22 years of hostilities was more important than what was said in the Communique itself. The joint issuing of the Shanghai Communiqué on February 27 marked the start of normalizing diplomatic policy after these two decades of conflict.