In relation to the monster ability web walker, in this case from a giant spider:
Web Walker. The spider ignores movement restrictions caused by webbing.
The only other mentions I can find of webbing is in the web spell:
Each creature that starts its turn in the webs or that enters them during its turn must make a Dexterity saving throw. On a failed save, the creature is restrained as long as it remains in the webs or until it breaks free.
A creature restrained by the webs can use its actions to make a Strength check against your spell save DC. If it succeeds, it is no longer restrained.
Do webs as a terrain feature need to be treated as if it was cast by the spell?
For example, if I want the spiders to have covered the floor with a thin (that is, not the absurd five feet deep as specified in the spell description) layer of web, only enough to obscure any pits etc, could that just be counted as difficult terrain? My intention would be to have the webs as a difficult terrain feature that lightly obscure the walls and floor, but not requiring saving throws to avoid being restrained as per the spell. The spider's web sense ability would still function as normal, and players could easily remove the web with fire and the like.