A buggy is a cart with wheels that's pulled by a horse. In the 19th century, the most popular way to take short trips was in a horse and buggy.
Most people think of a horse pulling a carriage when they hear the word buggy, although you can use the term for other small vehicles, whether they're electric or powered by gasoline — like a golf buggy. If you use buggy to describe a camp site, however, you mean it's infested with insects. The origins of both meanings are uncertain, although the Middle English bugge, "something frightening" might be one root of the "full of bugs" definition.