One of Mozart's most famous tunes, this piece is actually the final movement of his Sonata no. 11 for piano. The music imitates the music of Turkish Janissary bands (military marching music bands) with its steady strong tones with drums and cymbals, trumpets and bells.
When Mozart composed this piece in 1783, at the age of 27, the threat of the Ottoman empire for Europe, and especially Austria, was still there and the political atmosphere remained feverish and turmoiled after many years of battle between the Ottoman and Austrian Empires. In this music, Mozart's use of the style traditionally played by the Ottoman troops was therefore related with the overall political conflict between the two empires (remember that Mozart was Austrian) and the general threat that the muslim power represented for Europe and its religion (christianity). At that time, it was in fashion for European cultures to "westernise" some elements of the muslim culture, in an effort to "downplay" or come to terms with the threat by the muslims. Mozart was therefore following this trend when composing his music, which is also joyful and upbeat, probably signifying his wish for the victory of the Austrian empire over the Ottomans.