A recitative is a type of musical writing resembling a person reciting, rather than singing.
Typically it is written for singers, in operas, to narrate the story and introduce an aria, where the singer sings. It can be accompanied by the harpsichord only or by more instruments or the whole orchestra.
There is also the instrumental recitative which is similar to the vocal recitative but is written for instruments, rather than voices. A very famous example of instrumental recitative is in Beethoven's last movement of his ninth symphony.
Following the opera style, especially in Italy in the 19th century,
often used the instrumental recitative in their compositions for violin and viola. Paganini's Sonata for Grand'Viola and orchestra is opened by a Recitative followed by a set of variations.