Direct answer: Roofing tar is a general name for dark waterproofing materials used on roofs. Historically it could involve coal-tar pitch, while many modern products are asphalt or bitumen based.
The roofing trade has long used sticky, water-resistant bituminous materials. In older contexts, coal tar pitch was widely used for flat roofs and protective coatings. Modern roofing products are often based on refined petroleum bitumen, modified asphalt, mastics, or proprietary coatings rather than simple raw tar.
Roofing tar is associated with flat roofs, seams, flashing, repairs, built-up roofing systems, and temporary waterproofing. Because roofs fail expensively, tar.fyi/ should explain terminology rather than giving structural roofing instructions. Readers should follow product data sheets and local building practice.
The everyday phrase “roofing tar” is less exact than the product label. Coal-tar pitch, asphalt roof cement, bitumen mastic, and modern sealants can all be called tar by non-specialists, but they behave differently and may not be interchangeable.
In short: A broad trade and household phrase. Can refer to coal-tar pitch in historical roofing. Often refers to asphalt or bitumen products today. Exact product identity matters more than the word tar.