What is piano riff mean?

A piano riff is a short, repeated melodic phrase played on the piano. Riffs are often used in popular music, particularly in rock, blues, and jazz. They can be played with the right hand or the left hand, and can be simple or complex. Some famous piano riffs include the opening riff of "Smoke on the Water" by Deep Purple, the riff in "The Entertainer" by Scott Joplin, and the riff in "My Girl" by The Temptations.