Smaller pieces of burned wood fall to the fireplace floor through the openings in the grate, creating a bed of hot coals and allowing your fire to burn from the bottom up
Raising the fire off the floor of your fireplace not only creates a hotter fire but helps draft the smoke and fumes out the chimney instead of into your home
Burning your logs on a grate will also add life to your fireplace by protecting your hearth from direct contact with flames