That’s right. This is the piano suite "Pictures at an Exhibition", the representative work of the Russian composer Mussorgsky. It is the author's feelings and thoughts after visiting a painting exhibition. Therefore, the original work is a piano work.

French composer Ravel adapted this work for orchestral music in 1899, and it became a model of orchestral orchestration in the history of music. Orchestration courses for composition and musicology majors in later conservatories were required to study this adaptation of Ravel's piece in order to learn the matching and toning of the instrument parts.

Arr. in brackets is the abbreviation of Arranged, which means "adaptation". Therefore, the composer is Mussorgsky and the arrangement is Ravel. By the way, everyone is familiar with another masterpiece of Ravel, which is "Boleiro".