Conservatories and orangeries look very similar, so it can be hard to tell what their differences are. The main thing that distinguishes the two is the amount of glazing they have.
Conservatories usually have a roof that is made up of at least 75% glass. Orangeries, on the other hand, have roofs that are generally less than 75% glass.
Conservatories also tend to have walls that are made up of at least 50% glass. However, orangeries have glass on less than 50% of the wall area.
Orangeries were originally developed to grow oranges in large stately homes. Their mixture of brick and glazing gave the oranges a combination of plenty of sunlight and shelter.