It's a lifestock guardian dog. Those are a very, very specific set of dogs that bond to and guard sheep and goats; they do not herd and they don't really protect anything but the livestock they're bonded to.
LGDs are almost always white or mostly white (Anatolians, which are light tan, are an exception) and are EXTREMELY protective. They are other-dog and other-canid aggressive, will attack bears, will attack people if they think they threaten the sheep, etc., but are almost unbelievably kind and gentle to their livestock and to the humans they perceive as no threat (and to other dogs if they don't perceive any danger). They are also bred to ignore human commands if they think otherwise (after all, if you say come and there's a bear over the hill that you can't see, the dog should ignore you and run to face the bear).
A LGD's natural territory is in the hundreds or thousands of acres; they are not suited to small farms or yards, and will break or climb almost any fence to get out.
All in all, LGDs are rarely suited to family life, with the possible exception of SOME Great Pyrenees who have been bred away from stock for many generations. But the more primitive or fresh-out-of-the-mountains the dogs are, the less suited they are to being confined. Anatolians, Maremma, Akbash, and Kuvasz should only be owned by people prepared to meet their considerable needs.
