Concealment and cover are two totally different things. Yet Hollywood seems to get the two mixed up.
Concealment: You can't see through it. Walls, garbage cans, car doors, Bulletproof Human Shield, etc.
Cover: Stops bullets (and other projectile objects). Some concealment objects may stop bullets, depending on the object and the bullet. Others will not.
Hollywood seems to apply this trope most [...] [tvtropes.org]