BASH DAMAGE: Any attack made by a blunt object (fists, baseball bats; anything lacking an edge). Bash attacks reduce LP normally, and are the only attacks that can be used to knock out a victim.
SLASH/STAB DAMAGE: Any attack made by an object with an edge (knives, swords, claws, fangs, etc). The damage is doubled -after- subtracting any armor or similar protections. Edged weapons can be used to slice off heads or limbs. See the appropriate combat maneuver for those damage mods.
FIRE DAMAGE: When it comes to damage types, fire damage is the worst. Fire damage can scar terribly and heals slower than normal (half your normal rate). A person who has been set on fire takes six points of damage every Turn until they are put out. If more than twenty points of fire damage are inflicted, some scarring will occur.