The marimba is a type of keyboard percussion instrument.
It is similar to a xylophone, but the greatest difference would be its resonant sound, particularly in the lower register.
It has large resonators placed below the keys.
There are different types of marimba - traditional marimbas (diatonic - 1 row of keys) or concert marimbas (Chromatic - 2 rows of keys).
A concert marimbist normally performs with "mallets", often holding 2 of them in each hand.
They come with different materials, weight or hardness to produce different tones.
During the last 100 years or so, it has developed into a common instrument for ensembles or solo performance.
I perform a full concert marimba with an extended range of 5+3/4 octaves, made by Korogi.
My instrument is about 3m wide!