Production is the production of primary energy, i.e. hard coal, lignite, peat, crude oil, NGL, natural gas, combustible renewables and waste, nuclear, hydro, geothermal, solar and the heat from heat pumps that is extracted from the ambient environment. Production is calculated after removal of impurities (e.g. sulphur from natural gas).
Calculation of production of hydro, geothermal, etc. and nuclear electricity is explained in the Energy Statistics Manual available for free download on the IEA website.