A Smart Loot drop for a class will only roll the damage types this class can use, for instance, only Fire, Cold, Lightning and Arcane for Wizards.
In Diablo III, many items can roll increased damage of all skills of a specific damage type. In Diablo I and Diablo II, they were collectively named Magic Damage. Note that Arcane and Holy count as one damage type for the purpose of Resistance. Elemental Damage is a collective term for all seven (eight) major types of damage used in the Diablo series.
