Many tars can burn, especially when heated or exposed to flame, but flammability varies by type, temperature, vapours, and formulation. Tar should be treated as a combustible material unless a product sheet says otherwise.
Tar is linked with fire at every stage of its history. It is made by heating organic material, and many tars contain oily or resinous compounds that can burn under the right conditions. A cold, thick tar may not ignite like petrol, but that does not make it non-flammable.
The real risk depends on the material. Wood tar, pine tar, coal tar, bitumen products, solvent-thinned coatings, and roofing compounds can behave differently. Solvents and fresh vapours may create a greater fire risk than an old weathered coating. Heating tar can also release fumes that should not be treated casually.
This is one reason traditional tar work was usually done outdoors, in yards, forests, shipyards, or workshops with ventilation and experience. The older romance of tar barrels and smoky kilns should not hide the basic hazards of heat, smoke, sticky hot liquid, and combustible vapour.
For general readers, the safe answer is simple: tar can burn, and heated or solvent-based tar products deserve caution. Do not improvise heating, do not use tar near open flames, and treat the product label as more important than any general article.