Short answers, pulled from the story.
Joseph II was Holy Roman Emperor from the 18th of August 1765 and sole ruler of the Habsburg monarchy from the 29th of November 1780 until his death in 1790. He was the eldest son of Empress Maria Theresa and Emperor Francis I, and brother of Marie Antoinette and Leopold II. He is ranked alongside Catherine the Great and Frederick the Great as one of the three great Enlightenment monarchs.
Joseph II was born on the 13th of March 1741 at two in the morning in Vienna's Hofburg, and died on the 20th of February 1790, just shy of forty-nine years old. It is now believed he died of exudative pulmonary tuberculosis. He was buried in a plain copper coffin in the Kapuzinergruft in Vienna.
Joseph II issued over 6,000 edicts and 11,000 new laws, abolishing serfdom in 1781, issuing the Patent of Toleration in 1781, and making German the compulsory language of official business. He closed monasteries that did not teach or heal, redefined marriage as a civil contract, and made elementary education compulsory for all boys and girls. His policies are known collectively as Josephinism.
Joseph II's reforms provoked widespread unrest because subjects in the Austrian Netherlands and Hungary resented his centralization, Germanization, and interference in daily life. The Brabant Revolution drove out his officials and briefly created the United Belgian States, while Hungarian resistance forced him to withdraw many reforms before his death. His reckless foreign policy, including the Potato War and the Austro-Turkish War, also isolated Austria.
Joseph II was known as the Musical King and genuinely appreciated Mozart's music and admired his operas. He commissioned from Mozart the German-language opera Die Entfuhrung aus dem Serail. He was a supporter of the arts, including composers such as Wolfgang Amadeus Mozart and Antonio Salieri.
Joseph II was the brother of Marie Antoinette, Queen of France. After the French Revolution broke out in 1789, he sought to help the family of his estranged sister and her husband Louis XVI, and became involved in planning a rescue attempt. The plans failed, partly due to Marie Antoinette's refusal to leave her children behind and Louis XVI's reluctance to become a fugitive king.