This is a rather tricky carriage to pin down because I’ve seen all sorts of differing opinions on what it is and how to define it.
Originally, it was a very small one-person carriage that evolved from a sedan chair, which was an enclosed chair that was carried by four servants. It could be enclosed with a fixed or foldable head, though was often open to the air and had either two or four wheels. It was generally only used for going about town and not for long journeys and was often elaborately decorated. Frankly, there was a lot of variation between the designs, but the main identifier was that it was intended for a single passenger just like a sedan chair.
The name came from the word “chaise,” which is French for chair, so it would make sense that in its pure form, a chaise is a wheeled type of sedan chair.
However, it gets tricky when you search modern sources for the term chaise. A lot of bloggers, writers, and even encyclopedias define chaises in all sorts of terms beyond that original meaning. Some say it’s for two passengers, some say four. Some say two-wheeled, some say four-wheeled. Some had foldable heads. Some had fixed, unmoveable heads. Where other carriage types have specific identifying characteristics, there is no rhyme or reason to how these sources describe a chaise, which doesn't make sense. Each style of carriage has distinct characteristics that are different from others.
I believe this stems from a modern misunderstanding of the term "chaise" that was often used in primary sources from the 1800s. From what I can find, chaise was also used as another term for a coach or chariot. For example, a traveling chariot was also known as a "post chaise." And I found the term "hackney chaise" used by characters and people when referring to coaches and chariots that served as hackneys. So, when characters in books from that era refer to taking the chaise into town, they're generally referring to their coach or chariot -- not an official chaise.
Seats: 1 passenger