When docking, dogs' tails and ears are amputated. This is usually done for purely aesthetic reasons, which is why docking is now heavily criticized and has fortunately been banned in many European countries. In Germany, the law for ears has been in place since 1987 and for tails since 1998, although there is an exception for hunting use. Hunters use the risk of injury from undergrowth as a basis for docking dogs' tails.
The technique used for docking is associated with (often long-lasting) pain for the animals. In addition, your dog will have problems communicating after docking, as the ears and tail are important means of body language. After all, we are all familiar with the excited wagging of the tail when your four-legged friend is looking forward to his BARF or the tail tucking in when he is stressed or afraid.