Answer:
Etude is French for "study". A musical etude originally referred to a piece of music for solo instrument usualyy piano, intended to be practiced in order to gain techinical skill.
Well-known examples sill used for teching piano today are the etudes of Czerny and Hanon.
Chopin wrote etudes that are so full of musical interest that they are played and listened to for themselves, not merely studies to improve technique.
Liszt wrote a series he called "transcendtal"etudes, which again are valued as musical compositions in themselves, and so difficult to play that they are not of much value as exercises to improve technique, as the pianist has to already have a formidable technique in order to play them at all.