The following biographical information is from the Wikipedia article on Antonio Salieri:
Salieri was born August 18th, 1750 in Legnago, Italy. He studied the violin, the organ and the harpsichord in his childhood. He was orphaned early on and at the age of 15 he went to Venice under the patronage of the Mocenigo family. He studied the voice with Pacini and composition with Pescetti. In Venice he met composer and teacher Florian Leopold Gaßmann, who took him under his care and gave him a proper education. Eventually, they moved to Vienna. While attending concerts and musical gatherings with Gaßmann, Salieri became fast friends with the Emperor.
He slowly worked his way into the musical world and began to participate in varied and abundant musical gatherings for the Emperor. He continued his close friendship with the Emperor and performed him many favors, including daily music lessons. The Emperor also helped Salieri with the securing of a wife, whose father objected to Salieri due to the fact that the composer only made 100 ducats as court conductor. Hearing this, he raised Salieri's stipend to 300 ducats, and in return Salieri took over some of the duties of Kapellmeister Bonno, who was in his sixties and experienced poor health due to age and obesity.
Antonio was one of the "new school" opera composers and helped forge a new path for others to follow. In his career he composed over forty operas, most notably Tarare, Axur, re D'ormus, Les Danaides, Falstaff, La Grotta di Trofonio, Armida and La Locandiera. His large list of students includes musical greats such as Liszt and Beethoven.
He succeeded Bonno as Kapellmeister in 1788. He was President of the Tönkunstler Societät (a society of musicians' widows and orphans founded by Gaßmann in 1771) until 1818. He was also awarded a gold medal for civic valor on the occasion of the 50th anniversary of his stay in Vienna.
The biographer Alexander Wheelock Thayer believes that Mozart's suspicions of Salieri could have originated with an incident in 1781 when Mozart applied to be the music teacher of the Princess of Württemberg. Salieri was selected instead, because of his reputation as a fine voice instructor. In the following year Mozart again failed to be selected as the Princess's piano teacher.
Salieri fathered eight children and by all accounts was a decent man. He died in a state of delirium in a mental asylum in Vienna in 1825 at the age of seventy-five. On his death bed he begged loyal pupil Beethoven to tell the world that he was innocent of the crime of Mozart's death. Oddly, Salieri confessed to the poisoning days earlier, but his physicians reported that Salieri was delusional and probably suffered from advanced syphilis.
...the only thing I love in vocal music is truth, that truth which the incomparable Gluck makes me feel so profoundly throughout and in every detail of his Tragedies, and which I have felt on hearing works of other genres by a few other composers; so I strive to bring truth to all those of my operas which deserve such care...
Antoino Salieri to Carl F. Cramer, Vienna 20 July 1784
REGARDING THE FILM, AMADEUS
Some of the myths created by the film are the following:
a. Mozart and Salieri were arch enemies.
b. Salieri was jealous of Mozart's talent.
c. Mozart had an affair with Catarina Cavallieri, (who was actually Salieri's mistress). It is far more likely that Mozart's affair was with Anna "Nancy" Storace, who was his original Susanna in Figaro.
d. Salieri tried to sabotage Figaro. (He wasn't even in Vienna when Figaro was being staged. He was in Paris staging Axur.)
e. He murdered Mozart.
f. Mozart was an immature, giggling, drunken, ninny.
g. Salieri kept Mozart from getting a post with the Emperor.
h. Salieri was present when Mozart died.
i. Salieri had a hand in the penning of Mozart's Requiem.
The following is the delightful Cavatina originally sung by Nancy Storace in Salieri's La Grotto di Trofonio.