Can you provide an example of a riff in music and explain its significance in the overall composition?

A riff in music is a repeated pattern of notes or chords that serves as a catchy and memorable element in a song. An example of a famous riff is the opening guitar riff in "Smoke on the Water" by Deep Purple. This riff not only hooks the listener's attention but also sets the tone for the entire song, becoming a signature element that defines the overall composition.