Compared to the western forces, the Mongolain army had armor that was inferior to the west's. But this fact worked to the Mongol's advantage, because their armor was lighter. Their armor was mainly leather, covered with something like lacquer. The lacquer made the leather harder and more weather resistent because it added a protective coat to the leather. Other armies from the west usually used heavy chainmail that was bulky and a burden to carry. Their concept of light armor combined with speed from the light weight made the Mongol army nearly unstoppable. On the battlefield, the Mongols could travel faster and attack more fiercely without the clumsy chainmail.
The effects of their lightness could be found on a muddy battleground, where their opponents horses, bogged down with the rider's heavy chainmail, could hardly move through the mud. Because the Horse's hooves were sinking in the mud from the heavy weight, they were pretty much an easy target to Mongol archers.
The Mongols also had another type of armor, silk, from China. Silk is actually a very tough, yet soft and light, they wore it under their clothes. The silk "underclothes" doubled as light armor. If an arrow penetrated skin, the arrow could usually be pulled out by pulling at the silk, which was probably still intact.