In 1756, Wolfgang Amadeus Mozart was born in Salzburg into a family of musicians. His father, Leopold, was an excellent violinist and also wrote what was for many years the classic text book on violin playing. His sister, Maria Anna (whom he called Nannerl) was born 5 years earlier, and was already an accomplished clavier player. Mozart soon started to show a musical ability, and by the age of 3 was able to play the clavier. His ability to play grew in leaps and bounds, until he gave his first concerts at the tender age of 5. His father soon gave up his musical ambitions in favour of his child prodigy and the 2 of them (occasionally accompanied by Nannerl) began touring Europe, giving exhibition concerts to the great families of Europe. Their first port of call was Munich, in 1762, and then on to Vienna via Linz. It was here that a bout of scarlet fever struck the young boy down, and early indication of his continuing ill health. In 1763 they set out from Salzburg for Paris, where they stayed for 5 months. It was here that Mozart wrote his first published works - 2 sonatas for Clavichord. He was still only 8. The family continued to tour, moving on to London from Paris, where they arrived in 1764.
Mozart gave more concerts, demonstrating his mastery of the Harpsichord, and also composed his first 2 Symphonies - E flat (K 16) and D maj. (K 19). They remained in London for over a year, meeting a number of influential people, perhaps most importantly Johann Christian Bach (J S Bach's youngest son), with whom he struck up an enduring friendship. However, rather than returning home, they continued to roam Europe, visiting Paris (again), and a variety of places in Switzerland. They eventually arrived back in Salzburg in November 1766, 3 years after they set out.
Wolfgang continued to add to his repertoire of composition: some sacred music, a cantata, then in 1768 his first operas - "La Finta Semplice" (K 51) and a German Singspiel, "Bastien und Bastienne" (K 50). Throughout 1768 and 1769 he continued to play and write music and then at the end of 1769, Wolfgang and Leopold set out on another expedition - this time to Italy. They visited all the major cities in Italy in a tour lasting until 1771.
The rest of his childhood and early adulthood continued along the same theme - writing a variety of music, including symphonies, opera, church music and a numerous other pieces, and touring around the great houses and cities of Europe. The long term aim of much of this travel was to establish a position whereby Mozart could earn his keep. His father was Kapellmeister in Salzburg and Wolfgang would need to obtain a similar position were he to continue with his music. By the age of 21, this still hadn't happened, and he and his father were now on bad terms with the new Archbishop of Salzburg. Wolfgang therefore set out on another tour, this time with his mother accompanying him, since his father had to remain in Salzburg to pacify the Archbishop.
This time, the journey took Mozart and his mother to Mannheim, via Munich. It was at Mannheim that another key event in his life occurred: he met Aloysia Weber, with whom he fell deeply in love. She had an outstanding voice, and Mozart composed a great deal of music for her. However, his father was not at all happy with his choice of beloved and wrote to Wolfgang, insisting that he leave Mannheim at once, and without Aloysia. He duly did so, and progressed again to Paris. He wrote more music in Paris, including the D major symphony (K 297), nicknamed "Paris". However, his time at Paris affected his life significantly, since it was there that his mother died in his arms, in July 1778. He left the city a couple of months later. Meanwhile, Aloysia had married another, and he eventually returned to Salzburg an unhappy young man.
He continued to search for employment, much of his time being spent in Vienna, which he found far preferable to Salzburg. He continued to visit the Weber family, and this led to his marriage to Aloysia's younger sister, Constanze, in August 1782. In the same year he wrote his first great opera, "Die Entführung aus dem Serail". She soon became pregnant, and so started their continued battle against poverty. He continued to travel throughout his adult like, composing operas for the great opera houses of Europe. While he was in Vienna, he was forced to teach music and to beg from his Masonic friends in order to remain solvent. Despite this, his musical output remained prodigious. For example, his last 3 symphonies, (Nos. 39, 40 and 41 - "Jupiter") were written in six weeks in the summer of 1788. His health again began to fail him through 1789 and 1790, but despite this he continued composing new works. 1791 saw him working on some of his very greatest music - "The Magic Flute" and his Requiem. However, his ill health eventually got the upper hand and he died in bed in December 1791, whilst still working on the Requiem.
His funeral took place with few people present and the weather got so bad that none of the mourners (including Constanze) accompanied his coffin to its final resting place. He was buried in an unmarked pauper's grave, even his wife not knowing where.
Mozart wrote 40 or so symphonies (the exact number isn't clear, since some have been lost), the last one being No. 41, the Jupiter symphony. He wrote symphonies throughout his career, starting with a small orchestra and growing in confidence as he grew older. Mozart and Haydn were perhaps the two most important symphonic composers of their era. Haydn was even more prolific in his symphony writing, producing 104 in all. The composers knew each other well, each influencing the other with their own styles of symphonic writing.
The symphonies were written at a time when the genre hadn't acquired the magnificence of the Romantic period, being shorter and more regimented than, for example, Beethoven's masterpieces. For this reason, I wouldn't consider his symphonies to be his best music. Even the later ones are comparatively short (around 25 minutes) and lack the variety and depth of expression that some of his other music does. His later operas, for example, are amongst the greatest music written, and his Requiem can hold its own with any other pieces.