Shield bonus

Shield bonus is a bonus to Armor Class granted by a shield or by a spell or magic effect that mimics a shield.

Shield bonuses stack with all other bonuses to AC except other shield bonuses.

A magic shield typically grants an enhancement bonus to the shield's shield bonus, which has the effect of increasing the shield's overall bonus to AC. A shield bonus granted by a spell or magic item typically takes the form of an invisible, tangible field of force that protects the recipient.

A shield bonus doesn't apply against touch attacks.