What the title says. I get it that looting happens when the supply capacity of an area (and adjacent areas) is insufficient to provide for the monthly need of troops, but does looting actually give you anything? Does the stack that does the looting get a one-off increase in general supply? If yes, how large, does that too scale with the supply capacity of the area? If no, it would seem that looting, rather than allow armies to live off the land, would just be crapping in your own cereals as it severely reduces the supply capacity of the area and puts your balance of incoming and consumed supply even more in the red next turn.
Also, the manual says that troops never loot areas with 75% or more in loyalty. Does this mean they always succeed in their foraging rolls and can never starve there? Would seem rather strange.
edit: Forgot to ask, can units also loot adjacent areas, just like they can draw supply from them? I haven't seen it stated anywhere, but I've noticed looted symbols popping up all around when I've besieged cities in supply-poor environments.