Stagecoaches are often mentioned in historical fiction and sometimes in fantasy fiction. The stagecoach system was actually invented at about the time of the Renaissance, and allowed faster land travel than previous.
The term combines "coach" with "stage" - in a stagecoach system, the horses would be switched out for fresh ones at regular intervals. A stagecoach uses four horses (sometimes you will see "stagecoach rides" where they use two draft horses - this is not authentic) of a light harness or carriage type. Because the stages are kept short, the horses can be pushed to a faster pace without injuring or laming them.
The other key thing about stagecoaches was that they were the first carriages to have proper suspension. Stagecoaches were rendered obsolete by the growth of the rail network. They would run on a regular schedule. Their golden age was 1800 to 1830, when roads were improved and spring suspension invented.
As an etymological note, the dominance of the stagecoach is why we now use the word "coach" to refer to a long distance bus.
A stagecoach at the Wells Fargo museum in San Diego. Image source: Captain-tucker via Wikimedia Commons.