Wood is a natural resource obtained through assigning Trucks to tree harvesting and designating an area for tree harvesting. It is primarily used in the very early game as a source of Coal, from the early game as a component of Construction Parts and Household Goods.
Reserves of Woods on Home Island are clearly smaller than the demand till late game. You can use Sawmill for providing Woods after the ones on Home Island are drained.
Below are all the recipes, which contain this item. Note, that some of them may be locked behind Research, and not immediately available in your game.