The calorific value defines the energetic content of the materials; it is the amount of heat a substance produces after complete combustion. You can express it as the gross calorific value (GCV) or high heating value. Also, the calorific value of a substance (generally, solid biofuel or food) is the specific energy of combustion for a unit mass.
Net Calorific Value (NCV) also known as lower heating value (LHV) or lower calorific value (LCV) is determined by subtracting the heat of vaporization of the water vapour from the higher heating value. This treats any H20 formed as a vapor. Natural gas prices are decided on the basis of GCV and NCV.