A marimba is a percussion instrument consisting of a set of wooden bars tuned to different pitches, which are arranged and suspended similarly to a xylophone. The bars are struck with mallets to produce sound, and the instrument is typically played by one person.
A piano, on the other hand, is a stringed keyboard instrument, which has a set of keys that cause hammers to strike strings and produce sound. The piano can be played by one person, and can produce a wide range of sounds and melodies.
While both instruments are played with mallets, they are fundamentally different in terms of their construction, sound production, and musical capabilities. A marimba is primarily used for playing percussive melodies and rhythms, while a piano is used for playing more complex melodies, harmonies, and accompaniments.