A shield is a defence, typically of wood, that is used to deflect or block attacks aimed at the wielder.
DnD categorises them into 4 types:
- bucklers - small cicular metal shields
- light shields - roughly equvalent to a heater
- heavy shields - roughly equivalent to a Viking round shield or Roman scutum
- tower shields - a pavise
Interestingly the methods used to describe how they are wielded are almost completely wrong when compared to their historical basis. A buckler is held in the hand as is a heavy shield and light shields are strapped to the arm for horseman.