Skull Torches have a light level of 10, making them brighter than a Redstone Torch (7), but significantly dimmer that a normal torch (14). They are crafted differently from a regular torch, and they look like a sideways skull on the end of a shaft when placed.
Skull Torches can be used as an alternative to regular torches. However, sticks are more readily available than bones, so regular torches would be cheaper to make. They are mainly used for aesthetic purposes.