Technically there was a difference between dragoons and calvary. Calvary was supposed to fight on horseback while dragoons were supposed to ride horses to the battle and fight dismounted. But there were times when calvary fought dismounted and dragoons fought from horses.
The dragoons were equiped somewhat like light Infantry, with a short carbine, a hatchet, a pistol, and a shorter coat.
In the colonies, use of these kind of troops was limited because of the broken nature of most of the terrain. Only two regiments, the 16th and 17th Light Dragoons were brought to the colonies. These troops were mostly, but not always, used as scouts and messengers.