Definitely a difference. A tusk is a tooth which grows out from the mouth. Walruses, elephants and warthogs have tusks. A fang is a long pointed tooth in mammals. Tigers, lions, dogs, and wolves have fangs. In snakes they are the teeth which inject venom. We also say a spider has fangs for the same reason (though not technically teeth). These are both classified as types of canine teeth, which is why you're asking the question, I guess. Canines are the pointed teeth which many mammals have, and are generally pointed and used for holding food while tearing it apart. They are usually the largest teeth in a mammal's mouth. So for humans, we do have canine teeth but they are neither tusks nor fangs - unless we become vampires of course.

An elephant has tusks. (Also a walrus.) Canine is a kind of tooth, the sharp ones near the front. People have canines and probably some animals do too. Vampires have fangs! Also some snakes like cobras.

Thanks :)