Studded leather armor is a common item of equipment in most Fantasy Role-Playing Games.
Unlike leather armor, studded leather is made from soft unhardened leather. Your basic set of studded leather is a soft leather jacket with hundreds of metal rivets sewn into it. The rivets are what provide the protection, the leather itself exists merely as something to attach the rivets to. This form of basic armor provides good protection from slashing and cutting attacks. But is useless against bludgeoning weapons, and next to useless against arrows and other forms of piercing attacks.
Studded leather is very common among barbarians and the poor. Simply because it is very easy to make, even a simple housewife can make this armor with a day or two of work. Leather and rivets is the professional way to make this armor, but it is far from the only way to do it. Any sturdy cloth can serve as a base, and everything from standard rivets, to rings or even nails may serve as the studs. This armor is also very popular among sailors and pirates because it is the heaviest armor that still allows for easy swimming.
This armor does have the downside of wearing out rather quickly. Sweat and dirt have an effect on the leather similar to the effects it has on padded armor. While the studs tear out easily if the armor sees any real combat use. This armor has to be replaced frequently because it cannot be effectively repaired.