"Theme and Variations" is a musical form where a main theme is presented and then altered in various ways. Each variation maintains the essence of the original theme while introducing changes in melody, harmony, rhythm, or instrumentation. This structure allows composers to explore creativity while keeping a recognizable foundation. This form is commonly found in classical music, with notable examples by composers like Wolfgang Amadeus Mozart and Ludwig van Beethoven. It showcases the composer's ability to transform a simple idea into a complex and engaging piece, highlighting the interplay between unity and diversity in music.