The musical term Intermezzo has had a varied life.
It began in the sixteenth century as a light-hearted or comic interlude between parts of something larger and more dramatic or tragic. It could be musical, or a short comic play. From this, the comic opera, that popular art form that would be immortalised by the Strausses, Offenbach and Gilbert and Sullivan would grow. Short instrumental, orchestral or vocal acts, or even ballet scenes, were still performed between parts of larger works.
In 18th century Germany, an intermezzo began to appear amid the formal dance movements in a Suite, usually between the last two movements and in the 19th, composers such as Mendelssohn and Brahms used the term for movements within chamber works. Also in the 19th century, composers such as Schumann and Brahms cast it completely away from its original intent and used the term to describe an independent short piano piece that could just as easily been given the title Capriccio or Fantasia.
There are other names for it such as "Interlude" as in Benjamin Britten's Four Sea Interludes in the opera "Peter Grimes". Some composers have used the term, Entr'acte.
Intermezzo is the name of an opera by Richard Strauss.