The martial keyword indicates that the power source of a class or power is martial arts training and physical prowess.
Martial: Martial powers are not magic in the traditional sense, although some martial powers stand well beyond the capabilities of ordinary mortals.[PH:54]
Classes that draw power from the martial power source are:
Martial powers are also called "Exploits."
The other power sources are Arcane, Divine, Primal, Psionic, and Shadow.