Short answers, pulled from the story.
Michael von Puchberg was a Viennese textile merchant born on the 21st of September 1741 in Zwettl, Lower Austria. He is remembered primarily as the man who lent Wolfgang Amadeus Mozart approximately 1,400 florins across a series of loans during a financially difficult period in the composer's life.
Puchberg lent Mozart a total of approximately 1,400 florins, in individual loans ranging in size from 30 to 300 florins. The loans were made around 1788 through 1790 in response to twenty-one begging letters Mozart wrote to him.
Mozart had begun repaying the loans by 1791 but died on the 5th of December 1791 before settling the full debt. His widow Constanze, who became a successful businesswoman through memorial concerts and publications, repaid Puchberg in full several years after Mozart's death.
Mozart wrote twenty-one letters to Puchberg requesting loans, and their tone grew increasingly desperate over time. Early letters invoked the bonds of Masonic brotherhood; later ones, such as the letter of the 12th of July 1789, described his wife and child as at risk of ruin if Puchberg did not help.
Puchberg was a close friend of Joseph Haydn as well as Mozart. In 1790, Mozart invited only Haydn and Puchberg to attend rehearsals of Così fan tutte. When Haydn was in London and heard of Mozart's death, he wrote to Puchberg to express his grief.
The musicologist Michael Lorenz showed in 2009 that at the time Mozart described himself as destitute in letters to Puchberg, the composer was living in a spacious apartment on the Alsergrund costing 250 florins a year and owned a carriage and a horse. Lorenz concluded Mozart may have vastly exaggerated his financial problems to obtain the loans.