A hansom is an old-fashioned carriage that's pulled by a horse. There are still some cities where you can find a hansom to ride in for fun, but it's no longer the fastest way to get where you're going.
In the 1830s, the hansom, also called a hansom cab, was the latest way to get get around in busy cities. It was smaller than conventional horse-drawn carriages, which had four wheels and at least two horses. With only two wheels and a low center of gravity, hansoms were safe, light and agile, and could be pulled by just one horse. A man named Joseph Hansom patented what he dubbed the "Hansom safety cab" in 1834.