In the Old World you may obtain grain from farm tiles, meat from open range and water tiles,  wool from fertile hills, horses from horse corrals, and timber from dense and scrub forest tiles. You may find iron ore and copper in the hills or mountains, and tin in the swamps. All these items are called resources.

Early in the game you should rapidly increase the amount of these resources available to your workers and industry.  

Your explorer can search for hidden mineral resources. Your builder can construct developments on  terrain tiles so that the tile will produce resources for your Empire. Your engineer can build roads so that they are on the same tile with resources or adjacent to them. This allows any resources from the tile to be transported and used.