What is contrafact?

Context: Parker's style of composition involved interpolation of original melodies over existing jazz forms and standards, a practice known as contrafact and still common in jazz today. Examples include "Ornithology", and "Moose The Mooche". The practice was not uncommon prior to bebop, but it became a signature of the movement as artists began to move away from arranging popular standards and toward composing their own material. Perhaps Parker's most well-known contrafact is "Koko," which is based on the chord changes of the popular bebop tune "Cherokee," written by Ray Noble.

Answer: Contrafact is a type of jazz composition where the composer takes the basic structure of a popular song, rearranges it and provides a new melody to the song. Charlie Parker was a jazz musician and composer who used this style of composition extensively. Some of the best known examples of Parker's use of contrafact are:
"Ornithology"- Based on the popular song "How High the Moon"
"Moose the Moose"- Based on the standard "I've Got Rhythm"
"Koko"-Based on the swing standard "Cherokee"