Structures
In Red Alert 2 and Yuri's Revenge, Structures are BuildingTypes that are built from the Structures tab in-game. They have a BuildCat value of Power, Tech or Resource, or have no BuildCat set at all.
In contrast, Armory buildings are BuildingTypes with BuildCat=Combat, which makes them available on the Armory tab. Not to be confused with Armory.
Structures and Armory buildings are usually collectively referred to as "buildings".