Short answers, pulled from the story.
The International Military Tribunal began on the 20th of November 1945 and the verdict was delivered on the 1st of October 1946. Closing arguments were presented on the 31st of August 1946, after which the judges withdrew into seclusion.
Twenty-two surviving Nazi leaders were tried by the International Military Tribunal. Of the 24 originally indicted, Martin Bormann was tried in absentia, Robert Ley died by suicide before the trial began, and Gustav Krupp was too ill to stand trial.
Twelve defendants were sentenced to death, including Göring, Ribbentrop, Keitel, and Kaltenbrunner. Ten were hanged on the 16th of October 1946; Hermann Göring killed himself the day before his scheduled execution.
The Nuremberg trials marked what legal scholars call the true beginning of international criminal law by holding individuals, rather than states, responsible for breaches of international law. The trial established the precedent that crimes against peace, crimes against humanity, and war crimes could be prosecuted internationally. The United Nations General Assembly unanimously affirmed the Nuremberg principles on the 11th of December 1946.
The four charges were: conspiracy to commit crimes against peace, crimes against peace (planning and waging aggressive war), war crimes, and crimes against humanity. The last charge, crimes against humanity, covered murder, extermination, enslavement, deportation, and other inhumane acts against civilian populations.
The United States alone conducted twelve subsequent military trials in the same Nuremberg courtroom under Allied Control Council Law No. 10. These trials addressed 177 defendants drawn from an identified pool of 2,500 major war criminals; 142 were convicted and 25 sentenced to death. The trials covered doctors, judges, industrialists, SS members, and military commanders, generating 132,855 pages of transcripts.