Elephants use their tusks for a variety of tasks. Principally, they are formidable weapons against potential predators like the tiger (although tigers will only ever attack young or juvenile elephants) or in battle against other elephants. They are also used to aid foraging, digging, stripping bark and moving things out of the way; trained logging elephants are capable of lifting large logs with their tusks. There is also a display element to tusks and they can attract the interest of females.
Evidence suggests that elephants normally prefer one tusk over the other, similar to being left or right handed in humans. The preferred tusk is known as the master tusk.