Wood is a resource that's harvested from trees, six chops from the starter Axe can fell a tree, a further two chops will turn the tree in to smaller chunks (large logs) and then two more on each large log will give a generous amount of smaller logs. You can then collect these logs by pressing E and you'll also find that there's spare flat pieces of wood that're left over.  


 Rock is a resource that you can gather from large chunks of rock that are scattered throughout the map. You use the pick axe and hit the larger rocks 17 - 20 times, once it's broken up you'll be rewarded with eight pieces of rock.