Damage Types or "keywords" are used to express the power being used by their respective origin. Abilities will usually, not always, share mechanics when they share a damage type. Damage types are independent of origins and therefor can be categorized into any one freely.
The lightning damage type is grounded in movement. Lightning abilities usually involve movement as a core mechanic as well as the energy usage fluctuates dramatically. Power moves cost large amounts of energy but energy is constantly being replenished, usually through movement (ex: Static Charge)
The Fire damage type is categorized by the visual effect of flames. They usually incur instant damage and are known for their higher chance of critical strikes.
The physical damage type consists mostly of weapon attacks that can cause bleed effects and also effect armor mechanics. (ex: Bulwark) The visual look is usually steadfast or acrobatic and focuses on the body total movement.
The Affliction damage type consists of debilitating moves like debuffs, slows, DoT's, and drains and usually show a sickly or deadly visual element to them.
The Shadow damage type deals with deception, drains, and trade-offs. (ex: Dark Mantle) It is visually categorized by monotone and black colored abilities as well as abilities that hide or enshroud the user.
Radiance damage types are usually defensive in nature or support style moves like healing allies and helping others. These abilities have a focus on bright and beautiful visual effects.
Water damage types are usually control based or defensive abilities. They take advantage of the many forms of water like ice to help with crowd control and different scenarios.