Tar is modified resin produced primarily from the wood and roots of pine by destructive distillation under pyrolysis. It is a viscous black liquid. Production and trade in tar was a major contributor in the economies of Northern Europe and Colonial America. Its main use was in preserving wooden vessels against rot. The largest user was the Royal Navy. Demand for
tar declined with the advent of iron and steel ships.
Tar-like products can also be produced from other forms of organic matter such as peat. Mineral products resembling tar can be produced from fossil hydrocarbons including petroleum. Coal tar is produced from coal as a byproduct of coke production.
source: en.wikipedia.org/wiki/Tar Edit 
