A sonata is a long piece of classical music that's usually made up of several parts. A sonata can be played by an orchestra or just one instrument, like a piano.
If you're a classical music fan, you've probably heard sonatas played in concert halls or on recordings. Beethoven and Mozart famously composed sonatas for the piano, and modern composers continue to write sonatas for many different instruments. The Italian word sonata has come to mean "piece of instrumental music," although its literal translation is "sounded" or "played." This is in contrast to another Italian musical term, cantata, which means "sung," or "musical piece that is sung."