Wide dynamic range combines two or more exposures of the same scene so that bright and dark areas are both visible. It is measured in decibels, where a higher figure indicates more range. It matters where a camera faces a doorway, window or vehicle headlights.
A lobby camera facing glass doors sees a bright street and a dim interior at once. Without wide dynamic range, one of them will be a silhouette.
How the exposures combine
The camera captures a short exposure for highlights and a long one for shadows, then merges them. Hardware processing happens in the sensor, while software blending can leave halos around moving subjects.
When to enable it
Use it at entrances, loading docks and anywhere light varies sharply across the frame. On an evenly lit wall it adds processing and can soften fine detail without any benefit to the image.