Armor increases defense and can add immunities or raise stats. Humans and mutants can only wear one of each type of armor at the same time. Robots are not restricted by this limitation. Robots do not gain the defense or stat bonuses listed, however, they do gain immunities. Instead, robots gain the defense in the Robot Modifier stat column.
Shields do not directly increase the defense stat for humans and mutants. When they are equipped, they allow for certain enemy attacks and abilities to be blocked for one round; any physical hits that are not blocked deal reduced damage. Generally, most physical attacks can be blocked, but some non-physical attacks can be blocked as well. More expensive shields block attacks more often than less expensive ones.
As an added bonus, when a unit uses the Flame, Ice, or Dragon shields in battle, it creates a barrier that help protect the entire party against certain elements until the end of the battle.