1) There are two main types of termites in the US - drywood termites and western subterranean termites. Drywood termites infest wood directly while subterranean termites travel through the ground to structures.
2) For drywood termites, fumigation using sulfuryl fluoride gas is often the best treatment as it kills termites in both visible and hidden areas. Local treatments involve drilling holes and injecting wood with pesticides.
3) Western subterranean termites are treated through foundation applications of pesticides along the perimeter of structures or by trenching and treating along foundations to establish a pesticide barrier.