Wood

Wood is a consumable resource produced by Lumber Camps and used to expand cities as well as to construct ships, siege equipment, bridges, fortifications (camps) and building upgrades. Wood can be stored in camps or cities and transported via supply lines, but it cannot be carried by units.

You can see where your wood is moving and how it consumed in a building's trade tab. In the tab you can also set the building's stockpile level which causes it to automatically move wood from nearby buildings that have an excess supply. To see how wood is being consumed, produced and moved throughout your empire, click on the wood icon above the mini-map in the bottom-left corner of the screen.