Short answers, pulled from the story.
Joseph Stalin represented the Soviet Union, Harry S Truman spoke for the United States, and Clement Attlee joined as Prime Minister of the United Kingdom. Winston Churchill had been the British leader until a general election changed his position days before the conference began.
The leaders signed the Protocol of Proceedings on the 2nd of August 1945 after meeting from the 17th of July 1945. The document became known as the Potsdam Agreement and it was published on the following day.
Article 8 set the Oder-Neisse Line as Poland's provisional western frontier including territories like Pomerania and most of East Prussia. The final delimitation waited for a peace settlement that eventually came in 1990 when East Germany recognized this boundary in 1950.
Post-war Germany divided into four Occupation Zones controlled by Britain, the Soviet Union, the United States and France. Commanders-in-chief exercised sovereign authority over matters within their own zones while acting jointly through the Allied Control Council formed on the 30th of July 1945.
France refused to accept any obligation to abide by Potsdam Agreement in Allied Control Council proceedings and separated Saarland from Germany to establish its protectorate on the 17th of December 1947. Rising tensions between East and West led to Germany's rearmament and Cold War circumstances transformed what was meant to be temporary occupation into permanent division.