Termite shields are usually made of non-corrodible metal, placed in or on a foundation wall or other mass of masonry or around pipes to prevent passage of termites.
I don’t see termite shields often, generally they are found in pier and beam construction and sometimes slab. For houses that do have them, the chances of having termite damage go way down. However, shields do not remove the need to have annual inspections and or periodic preventive treatments.
The picture to the left is a metal termite shield on top of a concrete pier under a home.