Every zone belongs to a biome, which determines what kinds of wildlife is found there, as well as the availability of resources that can be gathered by players. Each biome contains three types of resources, with three levels of availability.
Primary resources are the most abundant, and certain zones will even be hotspots for that resource (displayed as a resource icon on that zone in the world map), making them excellent places to gather. Secondary resources are ones that can also be found in that biome but have no hotspot zones there. Tertiary will be scarce in this area.