Buildings:
Buildings are vital if you want to progress in this game. They get you resources and allow to take certain actions (research and train units or trade in a market). Available buildings:
Castle
Clay quarry
Sawmill
Ore mine
Warehouse
Shelter
Mill
Barracks
Wall
Market
Residence
Goldsmith
Memento

Build list:
If you want to build something, you have to select "Castle" from main menu. There you will be able to select which ones to build (or upgrade). After that, resources will be deducted and the selected process will be started. You can cancel that process at any time and get your resources back. Only one process is being done at a time, but you can add two more buildings to queue. They will be done one after another.