Dogs have tails for balance, but also to help them communicate. A dog’s two most common “tools” for communicating are his tail and ears.
The tail is a part of your dog’s spinal column which serves a very important role for balance. Greyhounds are known for their great speed but without the tail to serve as counter balance, they would simply fall over whilst running and attempt to turn a sharp corner.
The tail is also used to communicate with other dogs and if a dog’s tail is standing upgright then they are exercising his/her dominance over other dogs.