From Diablo Wiki
Physical is one of the types of damage in Diablo III.
Most types of weapons or open-handed attacks deal physical damage, as do most monster attacks.
Critical hits scored with physical damage deal double damage, but do not pack any other bonus effect.
 Damage Types
any change in the range of damage types to include holy, shadow, voodoo or anything else to match the classes? —Scyberdragon
Damage types will likely change some but are currently Physical, Fire, Lightning, Cold, Poison, Disease, Arcane, and Holy. —Diablo
Whats the difference between poison and disease damage?—WickedBubba
Disease has a damage debuff (both intake and output), and poison has a health debuff (regen/heal). Subject to change of course.—Diablo
Is there much difference between poison and disease? They’re both internal maladies that hurt over a period of time.—Grug
Fairly significant in their difference, but both countered with a single resistance. Damage/resists aren’t design complete though.—Diablo