I know the basics - they move faster than labourers and carry more pr. trip. And they pick up raw materials from mines, clay and sand pits and work/forester camps and deliver food to temporary shelters.
But are there any other things they do? I think I remember seeing that one had carried grain at one point in the past year, so do they pick up produce from fields too?
Food to temporary shelters, none of the food spoils and it counts as part of your food storage, your townsfolk starve despite there being months of food surplus.
I have seen them move a resource from one storage to another if the original storage was disabled and there was lots of it, alongside the horde of labourers
If you use your Storage Cart for stone and wood gathering, then return to the stockyard to empty the Cart when full, any Wagons available will help unload the Cart.
Taking large numbers of stone or wood in single batches, as opposed to the 1 and 2 items per townsfolks.