Both structures may be identical, but a greenhouse is for plants, while a conservatory is for human habitation. Originally designed around the 17th century, this structure was composed of stone columns and thin glass panes. It housed all the delicate plants the English brought back from exotic travels.
Closer to Victorian times the English adopted the word 'conservatory' to mean an external sitting room adjacent to the main house. Generally today a greenhouse is extant from the main house, while a conservatory is connected to the main house or building, such as a hotel, via a narrow or short walkway.
Conservatories gained popularity around the mid-19th century as the glass tax was lifted and wrought iron and steel became cheaper to source. The walls traditionally were composed of glass with metal reinforcements, but modern structures can be made of shatter-resistant plastic and cedar.
Shortly after spring cleaning commenced, the glass windows were polished, the floor scrubbed clean, and the tea service would be set up. A conservatory allowed the Victorian a sanctuary to get away from it all, without ever stepping foot in the street. The conservatory was generally closed up in the winter, the sumptous pillows and wicker furniture being cleaned and stored away until the next warm season arrived.
Queen Victoria's favourite conservatory was located at Chatsworth House, London. It took five years to build and covered over three quarters of an acre. It featured a tent-like shape, and was centrally heated and lit with twelve thousand lamps. The Queen declared, "It's the most stupendous and extraordinary creation imaginable". Queen Victoria wasn't around in 1920 to save it from being demolished. Costs were used for the war efforts, with its costly upkeep no longer justified.
If you don't have the space in your backyard to build a conservatory, the best place to see one is right in Victoria, BC. The Empress Hotel is home to one large connected conservatory, and was built with the hotel from 1904 to 1908. Take a lovely stroll in their English garden and forget about modern contrivances.