Quebracho is the name given to a family of trees native to South America. The parts of these trees that aren't used for making furniture often end up as lump charcoal.
The wood burns slowly and can reach very high temperatures while producing very little smoke and ash, making it a relatively clean, efficient heat source for grilling.
Quebracho charcoal also requires less fire maintenance. It may take a bit longer to reach your desired cooking temperature, but you'll have long-lasting heat suitable for grilling.