Conformation in dogs refers solely to the visible details of a dog's structure and appearance, which is defined in detail by each dog breed's written breed standard.
Breed standards are designed only to descibe the breed's history, purpose, temperament, and appearance. The breed standard is not a check list of requirements, but rather a description, giving a detailed word picture of an ideal dog of that breed.
A dog that conforms to most of the described items in its breed standard is said to have good conformation. There are no fixed rules for dog conformation, as dogs are the most varied in appearance of any animals, be it in size, shape, or behavior. Instead, conformation in dogs is based on the dog type from which the breed has developed, along with many details that have been added to the breed standard, purposes of which differentiate one breed from another.