Shields are one of the main components of combat in Absovlement. Other that dodging attacks, Shields are the main defensive item to help you on your runs. There are 3 different types of rarities of Shields in the game:

Common
Uncommon
Rare

Shields are great for a more tankier playstyle, each Shields has a limit on how much hits you can take before you get staggered. This limit is called posture, the higher the posture the more hits your Shield can take.