Wood is a tough resource that must to be obtained to get other items. It provides good protection, along with good cover for underground bases. However, an axe can break a piece fairly easily. Wood is known for its ability to allow creation of tools. Also you can use it for charcoal (smelted it in a furnace with wood). There are three types of wood: Birch, which is white coloured with black marks and Oak are found in all biomes, but the Pine,the darker wood, is found in Tundra biomes. You can craft any wood into wooden planks, but it will always be oak planks.