An opera house is a theatre building used for performances of opera. It usually includes a stage, an orchestra pit, audience seating, and backstage facilities for costumes and building sets.
While some venues are constructed specifically for operas, other opera houses are part of larger performing arts centers. Indeed, the term opera house is often used as a term of prestige for any large performing-arts center.
Italy is a country where opera has been popular through the centuries among ordinary people as well as wealthy patrons and it continues to have many working opera houses such as Teatro Massimo in Palermo (the biggest in Italy), Teatro di San Carlo in Naples and Teatro alla Scala in Milan. In contrast, there was no opera house in London when Henry Purcell was composing and the first opera house in Germany, the Oper am Gänsemarkt, was built in Hamburg in 1678, followed by the Oper am Brühl in Leipzig in 1693, and the Opernhaus vorm Salztor in Naumburg in 1701.
In the 17th and 18th centuries, opera houses were often financed by rulers, nobles, and wealthy people who used patronage of the arts to endorse their political ambition and social position. With the rise of bourgeois and capitalist social forms in the 19th century, European culture moved away from its patronage system to a publicly supported system.
Early United States opera houses served a variety of functions in towns and cities, hosting community dances, fairs, plays, and vaudeville shows as well as operas and other musical events. In the 2000s, most opera and theatre companies are supported by funds from a combination of government and institutional grants, ticket sales, and private donations.
In the 19th-century United States, many theaters were given the name "opera house", even ones where opera was seldom if ever performed. Opera was viewed as a more respectable art form than theater; calling a local theater an "opera house" therefore served to elevate it and overcome objections from those who found the theater morally objectionable.
Opera was always popular among ordinary people as well as among the rich, so that there was a large audience available.
The term 'opera house' is indeed misleading, and intentionally so; it provides a veneer of social and cultural respectability and avoids the stigma of the title 'theater.'