Tar is made from organic material that has been heated in a low-oxygen setting, most commonly wood, coal, peat, or other carbon-rich matter. The exact answer depends on the type of tar being discussed.
The word tar is simple, but the material is not always the same. Pine tar begins with pine wood, roots, or stumps. Birch tar begins with birch bark. Coal tar comes from coal during high-temperature processing. Older writing may also use tar for thick fossil hydrocarbon materials, though modern writers usually separate true tar from bitumen and asphalt.
Most tars are products of heating rather than ordinary burning. In open fire, much of the material becomes ash, flame, smoke, and gases. In tar-making, the material is heated with limited oxygen so it decomposes and releases heavy liquids, oils, vapours, and residues. Those liquids can be collected and used, refined, or further processed.
That is why tar can be smoky, sticky, dark, and chemically complicated. It contains many substances from the original material, transformed by heat. Wood tars often contain smoky phenolic compounds and plant-derived fractions. Coal tar contains a different range of aromatic compounds because coal began as ancient plant matter altered over geological time.
For a reader trying to identify tar, the source matters more than the colour. A tin of traditional wood tar, a roofing product, and a historical reference to coal tar may all be black and sticky, but they should not be treated as the same material. The safest first question is always: made from what?