A depth API gives an application access to information about distances in a scene, which can help it relate digital content to physical surfaces.
Distance is different from colour
A camera image describes appearance. A depth map estimates distance for positions in the image. A system may derive this information from camera motion, a depth sensor or a combination of inputs; LiDAR is not the only possible source.
What depth can help with
Depth information can support effects such as hiding a virtual object behind a real surface. It may also help with placement or interactions, depending on the API. A depth map is not automatically a complete, accurate model of the room.
An exhibition example
If a visitor walks behind a plinth, the experience might hide the appropriate part of a virtual sculpture. This requires the viewer to support and use the relevant depth information. Do not assume that every AR platform or browser offers it.
What to verify
Depth quality and availability vary. Test the actual device and environment, especially around edges, glass and reflective surfaces. ARCore's Depth API and web depth-sensing interfaces are distinct implementations with their own requirements.