Dropsite

After your units have gathered resources, they must deposit them at a dropsite before you can make use of those resources. All civilizations have several dropsites.

The Civilization Center is the most important of the dropsites, as it also can train basic units and expand it's owner's territory. Civilization Centers accept all resources.

Players can also build Storehouses and Farmsteads. These smaller buildings are cheap to construct and allow your Citizen Soldiers and Female Citizens to deposit resources without traveling all the way back to the Civilization Center. The Storehouse accepts stone, metal, and wood as well as being a place to research gathering technologies related to those three resources. The Farmstead accepts food and is a place to research technology that improves fields.

Docks also function as resource dropsites. Not only can Fishing Ships deposit their catch there, but Citizen Soldiers can also deposit any carried resources there. Docks are one of the few buildings that can be built in neutral territory, and, apart from the Civilization Center, they are the only dropsite that can be built in neutral territory.

The Mauryans also have a special unit, the Worker Elephant which acts as a mobile dropsite that accepts food, wood, stone, and metal.

From the Wildfire Wiki