Once exclusively musical term, divertissement formerly described a set of entertaining musical pieces for an ensemble or a chamber orchestra. Later, it also started to apply to the dances created for such music.
Divertissement piece is put into ballet shows for entertainment only and does not influence the plot of the story. Such practice came from French court tradition and had been sustained up until the 20th century. Divertissement’s main purpose is to amuse the spectator, but it may also strongly suggest historical and ethnic context of the story.
The most typical motif for a divertissement is a national dance (sometimes of a fictional nation). Since ballet was formerly a form of art mostly maintained by the ruler, such pieces would often reflect his political ambitions and even serve as a mean of propaganda. For example, in 1864, French ballet master Arthur Saint-Léon created an impeccable play based on a Russian fairy tale “The Little Humpbacked Horse”. The last act featured the dances of 22 different nations, all as one praising the tsar.
Another reason why divertimento took root in ballet shows were the danseuses, as they considerably displaced danseurs during Romantic era. Some variations were being specifically altered in order to make female soloists look better. Thanks to divertissements, the plays started including dances of the fairies, gemstones, pearls etc.