Short answers, pulled from the story.
Ostpolitik is the German word for eastern policy. It describes West Germany's effort, beginning in 1969, to normalize relations with the communist governments of Eastern Europe through engagement rather than isolation. Chancellor Willy Brandt, who won the 1971 Nobel Peace Prize for the policy, believed that trade and contact would gradually undermine communist authority over the long term.
Egon Bahr laid the intellectual groundwork with a 1963 speech at the Evangelische Akademie Tutzing, proposing the concept of "change through rapprochement." Bahr was a close ally of Willy Brandt, who implemented the policy after becoming the fourth Chancellor of West Germany in 1969.
The Hallstein Doctrine was a West German policy, upheld by Christian Democratic governments from 1949 to 1969, that severed diplomatic ties with any country formally recognizing East Germany. Its first application came in 1957, when West Germany withdrew recognition from Yugoslavia. Ostpolitik replaced this strategy of isolation with direct engagement.
The Basic Treaty, signed on the 21st of December 1972, established formal relations between the two German states for the first time since partition. The ambassadors exchanged were called "permanent representatives" for political reasons. The treaty also cleared the way for both German states to join the United Nations.
In April 1972, CDU opposition leader Rainer Barzel called a parliamentary constructive vote of no confidence against Chancellor Willy Brandt. Barzel came two votes short of the majority needed. It later emerged that the East German government had paid two CDU deputies to vote against Barzel's motion.
Pope Paul VI pursued Vatican Ostpolitik from 1963 to 1978, engaging Soviet authorities to improve conditions for Christians behind the Iron Curtain, and receiving Soviet Foreign Minister Andrei Gromyko at the Vatican in 1966 and Soviet head of state Nikolai Podgorny in 1967. South Korea named its 1980s engagement policy toward North Korea "Nordpolitik" in direct allusion to the West German approach. The Democratic Party of Korea later extended this logic with a successor concept called the Sunshine Policy.