An impresario is a promoter: someone who books, promotes, and organizes shows such as concerts.
Impresario comes from an Italian word for a businessperson, and in English it especially refers to someone in the promotion business. In the music business, Bill Graham was a famous impresario who arranged concerts for huge bands such as The Rolling Stones and Pink Floyd. An impresario signs a band — or other entertainment — and makes a deal with the venue. Impresarios then arrange advertising and promotion to alert fans and arrange for tickets to be sold. Impresarios make shows happen.