There are several types of tools within Planet Explorer as well a several general quality levels.
Axe: Axes are specialized in cutting trees and gathering wood. They also have a greater felling speed as well as more wood gain per tree then the starting knife.
Pickaxe: Pickaxes are specialized in mining ores from the ground and have a better ore to dirt gain ratio than shovels.
Shovel: Shovels are specialized in digging dirt and stone types and have a higher dirt/stone type gain compared to a pickaxe.