A backdrop appears behind all other surfaces in an app, displaying contextual and actionable content. A backdrop is composed of two surfaces: a back layer and a front layer. The back layer displays actions and context, and these control and inform the front layer’s content.
A backdrop consists of a back layer, a front layer, and an optional subheader. Either the back layer or the front layer can be active at a time. The back layer can be concealed by either interacting with the the front layer or tapping a conceal affordance on either layer.