The "theme and variations" is a musical form where a main theme is presented and then altered in subsequent sections. Each variation modifies the original theme through changes in melody, harmony, rhythm, or instrumentation, while still retaining its recognizable essence. This structure allows composers to explore creativity within a defined framework. This form is commonly found in classical music, with notable examples by composers like Ludwig van Beethoven and Wolfgang Amadeus Mozart. It provides a way to showcase a composer's skill in developing ideas and can be seen in various genres, including jazz and popular music.