Firewood is any wooden material that is gathered and used for fuel. Generally, firewood is not heavily processed and is in some sort of recognizable log or branch form, compared to other forms of wood fuel like pellets. Firewood can be seasoned and heat treated (dry) or unseasoned (fresh/wet). It is generally classified as either hardwood or softwood.
Stack of firewood next to a building
Stack of split firewood and a splitting maul, Czech Republic
A Woman of Ōhara Carrying Firewood, Japanese painting by Nagasawa Rosetsu (1754–1799).
Firewood collector in Mozambique
A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but has since also been applied to other sources of heat energy, such as nuclear energy.
Firewood was one of the first fuels used by humans.
Wood as fuel for combustion
Coal is a solid fuel
A filling station