A vernissage is a preview of an art exhibition, which may be private, before the formal opening. If the vernissage is not open to the public, but only to invited guests, it is often called a private view.
There is a comparable ceremonial ending of art exhibitions, called a finissage, from the French word meaning "finishing". Larger art exhibitions may also have an event halfway through their residency called a midissage. These latter terms are rare in English; they are more commonly used in German and Dutch but not in French.