Direct answer: Swedish tar is usually pine tar from Sweden or a Swedish-style pine tar associated with traditional wood, rope, and maritime preservation.
Sweden became famous for tar because forest districts could produce it from pine roots and timber, while ports handled its export. Historical Swedish tar production involved rural labour, tar-burning grounds, barrels, and long trade networks serving shipyards and merchants.
Swedish tar is used as a heritage material for boats, log buildings, fences, exposed timber, and craft projects that call for a traditional northern finish. It is also a key phrase in naval stores history because tar was once a strategic material.
Swedish tar overlaps strongly with Stockholm tar. The difference is that Swedish tar points to country or style, while Stockholm tar points to a famous trade name and perceived grade. Both are normally discussed as pine wood tars.
In short: Usually a pine wood tar. Historically important in Scandinavian export trade. Used on wood, rope, and maritime materials. Closely related in meaning to Stockholm tar.