The Dwarven Laborers are sturdy lads who have no love of orcs, but their skill in combat is lacking and are more likely to hit themselves or an ally if they ever engage in combat. For that, they participate in the war effort by fueling the fires of the Dwarves to allow them to forge more weapons.
Anything wooden must expect no mercy from them; they may not be able to swing their axe against a swift target, but they can make quite a dent in slow or immobile ones. Ents and trees should fear their wrath.
Each Dwarven Laborer that you train will automatically start looking for trees to cut down with his axe, first hacking them down and then carrying the logs back to the lumber mill. Initially, each log that a laborer brings back will yield 6 resources, but if you upgrade the production of a lumber mill, this yield will increase.
In addition, lumber mills provide a nice discount, so building a couple of them can heavily reduce the cost of Siege Weapons and Battle Wagons.
"What do we need built?"
"We've got things to build."
"Alright, let's go!"
"Where do I go with these?"