When speaking of wood as fuel, it's helpful to think of two words - Cured and dry.
In our area People often sell wood saying it is dry because it was cut a year ago.
In fact this wood is cured because all sap and natural moisture is gone. However if the wood has not been
covered it is still wet.
When you burn wet wood or green wood you lose heat value up the flue as the heat requied to convert this moisture to steam will go up the flue with the steam. If the steam condenses in the flue it will result in cresote deposits on the chimney walls(cresote is carried on the steam droplet).
If you air dry your wood you can then get the fire box temps high enough to burn the cresote in the
firebox. The resulting heat is used to heat your home, rather than evaporate the moisture in the wood.
The new clean burning stoves make this much easier and as a result put more heat in your home.