Defence is the ability to reduce te amount of damage you take. There are 4 types of attacks and defence to match: Normal, Piercing, Elemental, and Shadow. One type of deffence will not lower all the damage you take (shadow defence protects only against shadow attacks. ect.)
Resistance is the ability to resist status effects. There are 7 status effects: Stun, Fire, Freeze, Shock, Poison, Sleep, and Curse. There can be a positive resistance and negative resistance. Where positive resistances help block status effects, negative resistances make you more vulnurable to them. Negative resistance usualy occurs when there is a positive resistance of a different type on the same item.