Short answers, pulled from the story.
The Treaty of Fontainebleau was an agreement signed on the 11th of April 1814 between Napoleon and representatives of Austria, Russia, and Prussia. It ended Napoleon's rule as emperor of the French and sent him into exile on the island of Elba, which was established as a separate principality under his rule.
Napoleon first offered a conditional abdication in favour of his son with Marie-Louise as regent, but the Coalition rejected it. Emperor Alexander argued that Napoleon's presence would always threaten peace in Europe. With no military option remaining after Marshal Marmont's corps surrendered, Napoleon issued an unconditional abdication renouncing the thrones of France and Italy for himself and all his heirs.
The treaty's 21 articles stripped Napoleon of imperial power while allowing him and Marie-Louise to keep their titles. Napoleon was exiled to Elba with 400 personal guards and had to surrender his French estates and all crown jewels. Marie-Louise received the Duchy of Parma and Piacenza and the Duchy of Guastalla. Empress Josephine's annual income was set at 1,000,000 francs.
Castlereagh refused to sign on behalf of the United Kingdom because doing so would have recognised Napoleon's legitimacy as emperor of the French. Britain also objected to exiling Napoleon to an island over which he had sovereignty, so close to France and Italy, fearing it could easily lead to renewed conflict.
The three signatories on Napoleon's behalf were Caulaincourt, Duke of Vicenza; Marshal MacDonald, Duke of Tarentum; and Marshal Ney, Duke of Elchingen. The allied signatories were Prince Metternich, Count Nesselrode, and Baron Hardenberg.
A copy of the treaty was stolen from the French National Archives between 1974 and 1988 by John William Rooney and Marshall Lawrence Pierce. The theft came to light in 1996 when a curator discovered Pierce had put the document up for sale at Sotheby's. The document was returned to France by the United States in 2002.