Backdrop
A backdrop, in interface design, is a layer behind the main content that displays context or controls related to what appears in front
What it means, how it is used and where it comes up, with its related concepts.
What it is and how it works
In Material Design 2, the backdrop was a component made up of a back layer, holding navigation, filters or settings, and a front layer with the content. When the back layer was revealed, the front layer moved down but stayed visible, and actions at the back changed what was shown at the front, for example by filtering a list.
Material Design 3 does not include this component and handles those cases with bottom sheets, panes or menus. More generally, “backdrop” also refers to the semi-transparent layer that dims the background when a dialog opens; CSS has a ::backdrop pseudo-element for styling it.
Also known as
Back layer