Conservatories, are usually built as extensions outward of your home, or place of business. Mostly asthetic, they provide more space to live or work in. This space is usually lighter, for the conservatory will have windows around every panel.
Modern conservatories are either custom designed, for the needs of the location, or modular, for DIY and ease of installation. The the former being constructed from a wide range of materials, ranging from solid wood, to metal to PVC frames. The latter being mostly of PVC plastic, for ease of manufacture. These PVC conservatories are simple to construct and are favoured by the rabid DIY enthusiast.
Originally, conservatories were used in days gone by, to keep a selection of rare fruits from far away places. The windows would create a type of 'greenhouse with seating', for the members of the house to enjoy a airy and calm reading space, for example.
Today, they are still used as light extension to a modern home, and come in various flavous. Some of their names still reflecting the era when that style became popular.
Victorian conservatories are square at the point where the meet the house, with the edge facing away from the house 'curved'.
Edwardian conservatories are square, with a pointed roof.
Lean-to Conservatories, sometimes called traditional conservatories, are simple square conservatories, with a sloped roof.