What is a piece for solo instrument accompanied by the orchestra is?

A piece for solo instrument accompanied by the orchestra is known as a concerto. In a concerto, the soloist plays a prominent role, showcasing their virtuosity and expressiveness, while the orchestra provides harmonic support and texture. This form typically consists of multiple movements, often highlighting contrasting tempos and moods, and is a popular genre in Classical Music. Examples include concertos for violin, piano, and cello, among others.