Wood is one of the main resources in which you use to keep your settlement growing. The main use of wood is to construct buildings and Wonders. Wood can be obtained by constructing a Logging Camp on forest tiles. It is booseted by a Sawmill. Additionally, it can be received as a trade from other players, or another one of your settlements by using a Customs house. You may also received 100 wood from the random resources each one of your wonders create daily and some tasks offer wood as a reward as well. In the Imperial Age, wood is made obsolete and is replaced with Coal.
Wood is a very useful resource in the Classical Age, Feudal Age, and Renaissance Age, because it is no longer used in the later ages. Therefore, building a settlement that produces more wood can be helpful during the early stage. Another way is to capture wood tiles on the map.