Field (Heraldry)
From AmtWiki
In heraldry, the background of the shield is called the field. The field is usually composed of one or more tinctures (colours or metals) or furs.
In extremely rare cases, the field (or a subdivision thereof) is not a tincture, but may be a landscape. Landscape fields are regarded by many heralds as unheraldic and deprecated, as they cannot be consistently drawn from blazon.