The AKC has developed a written description for every breed of dog they recognize in the USA as a pure bred dog. It describes the physical characteristics of the dog (acceptable colors, markings, size, bite, etc.) as well as the desired temperament. This document may also list certain undesireable characteristics that would cause a dog to be disqualified in competition.
This description is called the Breed Standard. It is different for each breed of dog. Obviously, the Breed Standard for a Great Dane won't work for a Chihuahua.
The Breed Standard for the Golden Retriever can be seen on the AKC website:
If may also be helpful to look at this diagram of a Golden, provided by the Golden Retriever Club of America (GRCA). It will help to explain some of the terms that are frequently used when describing the physical features of Goldens.
Click here for a larger view.