Carrying a shield provides additional protection. Carrying a shield requires one free hand, so it’s not possible with two-handed weapons.
Shields can absorb an attack but can only do so a few times.
Bucklers are small, circular shields. They can negate a single non-critical attack before they break.
Kite shields are tall curved shields. They can negate two non-critical attacks before they break.
Tower shields are very large shields capable of shielding the entire body. They can negate three non-critical attacks or a single critical attack before they break.