Wood
European Commission - Eurostat

Food and Agriculture Organisation (FAO)
Fuelwood or firewood includes "wood in the rough" in small pieces (fuelwood), chips, epllets and powder derived from forests and isolated trees, as well as good by-products from the timber industry and recovered wood products. They conserve the original basic structure of the wood and can be used either directly or after conversion into another woodfuel, such as charcoal. When needed, fuelwood can be converted into more convenient products, such as chips and pellets, without major chemical-physical processing.

Chips: wood in the rough that has been deliberately reduced to small pieces, or residues suitable for energy purposes.

Wood pellets: can be considered a fuel derived from the self-compaction of woody material from the combined application of heat and high pressure in an extrusion machine.

For information, there is also a broad range of liquid and gaseous fuels derived from fuelwood and charcoal basically by pyrolytic or enzymatic processes, such as pyrolysis gases, ethanol, methanol, products of growing interest but to date not as important as energy commodities. They are referred to other wood fuels.

International Energy Agency (IEA)
Covers purpose-grown energy crops (poplar, willow etc.), a multitude of woody materials generated by an industrial process (wood/paper industry in particular) or provided directly by forestry and agriculture (firewood, wood chips, bark, sawdust, shavings, chips, black liquor etc.) as well as waste such as straw, rice husks, nut shells, poultry litter, crushed grape dregs etc. Combustion is the preferred technology for this solid waste. The quantity of fuel used should be reported on a net calorific value basis

United Nations Economic Commission for Europe (UNECE)
Covers purpose-grown energy crops (poplar, willow etc.), a multitude of woody materials generated by an industrial process (wood/paper industry in particular) or provided directly by forestry and agriculture (firewood, wood chips, bark, sawdust, shavings, chips, black liquor etc.) as well as waste such as straw, rice husks, nut shells, poultry litter, crushed grape dregs etc. Combustion is the preferred technology for this solid waste. The quantity of fuel used should be reported on a net calorific value basis

UNSD Energy Statistics Section
Fuelwood - all wood in the rough used for fuel purposes. Production data include the portion used for charcoal production, using a factor of 6 to convert from a weight basis to the volumetric equivalent (metric tons to cubic metres) of charcoal.