The term refers to the temporary effect of shading, lightening or blurring, applied to any surface of the interface. The word ‘scrim’ came from photography, and means an element, which physically covers lights to make lighting effects. The effect that the scrim does, help to direct attention to other parts of the interface, while the surface under scrim remains available for interaction.
Scrims are used for dialog windows, navigation drawers, push-notifications, and backdrops.