Short answers, pulled from the story.
The CSCE was a Cold War diplomatic forum that recognized postwar European borders and established mechanisms for reducing political and military tensions between East and West while improving human rights in the Communist Bloc. It did not have the force of a treaty. In 1994 it was succeeded by the Organisation for Security and Co-operation in Europe (OSCE).
The Helsinki Accords were signed on the 1st of August 1975 at Finlandia Hall in Helsinki, Finland. Thirty-three European nations, the United States, and Canada signed the final document, covering 35 heads of state in total.
Finland proposed hosting the conference because President Urho Kekkonen saw a genuine negotiating forum as a way to stabilize political tensions in Central Europe after the 1968 Soviet occupation of Czechoslovakia. Finland held a diplomatic advantage because it had not formally recognized either West or East Germany, allowing it to manage relations with both countries from a neutral position.
All European countries except Albania and Andorra attended, along with the United States and Canada, amounting to 35 heads of state. Notable participants included Leonid Brezhnev, Gerald Ford, Harold Wilson, Helmut Schmidt, Erich Honecker, Pierre Trudeau, and Josip Broz Tito. Agostino Casaroli, Cardinal Secretary of State of the Holy See, chaired the final phase.
The final document was divided into four sections: the first addressed European security issues and border integrity, the second covered cooperation in economy, science, and environmental protection, the third concerned humanitarian cooperation, and the fourth set out arrangements for follow-up meetings and future conferences.
After the Soviet Union broke apart, it was widely believed that the third section of the Helsinki Accords, which addressed humanitarian cooperation, had quietly undermined the totalitarian system. Jimmy Carter made human rights a key objective of US foreign policy partly in response to the CSCE commitments, leading to clashes with the Soviet Union at follow-up meetings in Belgrade in 1977 and Madrid beginning in 1979.