Everything from front to back is sharp, so a lot of information shows in one frame at once.
When two layers must both show, like a product in the foreground and a person in the background; landscapes.
Public AI example available — Veo 'Deep depth of field'
Deep focus at f/11, everything sharp from foreground to background, a chessboard with a half-finished game in the foreground, a grandfather reading in the middle, a rainy window far behind, locked-off camera, 28mm lens, soft window light, calm mood, 6-second shot.
deep focus, everything sharp from foreground to background, f/11