Short answers, pulled from the story.
Christoph Willibald Gluck was born on the 2nd of July 1714 in Erasbach, a village in the Upper Palatinate that was part of the Holy Roman Empire. He was baptized on the 4th of July 1714 in the village of Weidenwang.
Gluck's reforms, codified in the 1767 preface to Alceste, eliminated da capo arias, vocal improvisation, and long melismas, while replacing dry secco recitative with accompanied recitative and linking the overture to the drama. His goal was to make words and music equally important and subordinate all elements to the drama rather than to star singers. These changes shaped Mozart, Weber, Wagner, and Berlioz.
After the premiere of Iphigénie en Aulide on the 19th of April 1774, Gluck's opponents brought the Italian composer Niccolò Piccinni to Paris to champion Neapolitan opera against Gluck's reforms. Paris divided into warring camps of "Gluckists" and "Piccinnists". The composers themselves took no part in the debate, though Gluck destroyed his draft of Roland when Piccinni was asked to set the same libretto.
Iphigénie en Tauride, which premiered in 1779, is often considered Gluck's finest work. It was a great success on the Parisian stage and was composed during the peak of his career there.
Gluck was Marie Antoinette's music teacher in Vienna, where she learned harp, harpsichord, and flute under him. When she became patroness of the Paris Opéra in the spring of 1774 after marrying the future Louis XVI, she took Gluck under her formal patronage and secured him a contract for six stage works.
Gluck took Salieri as a protégé when Salieri arrived in Vienna in 1767 and later brought him to Paris. He gave Salieri the libretto for Les Danaïdes and announced the opera as a collaboration. After its overwhelming success on the 26th of April 1784, Gluck revealed to the Journal de Paris that the work was entirely Salieri's.