Seasoned wood is wood that has been cut and split and has been sitting outside in a dry area (preferably covered, off of the ground and stacked so there is a lot of air flow), for a full year. Dry wood burns hot, emits less smoke and creates less creosote. Wet wood, when burned, must release water stored within the wood. This cools the fire, creates creosote, and hampers a complete burn. Ask any experienced wood burner and they will agree: dry wood is crucial to good performance. Seasoned wood normally has about a 20% moisture content. There are moisture meters to test wood but generally knocking two pieces of seasoned wood together will sound like a clear "knock", not a "thud". Properly seasoned wood will normally have cracks on the ends of the split logs and will be much lighter in weight than wet ("green") wood.