Few qualities of Labrador retriever

Show standards
Like any animal, there is a great deal of variety among Labs. These characteristics are typical of the show-bred or bench-bred lines of this breed in the United States, and are based on the AKC standard. Significant differences between US and UK standards are noted.
Size: Labs are a medium-large but compact breed. They should have an appearance of proportionality. They should be as long from the shoulders back as they are from the floor to the withers. Males should stand 22.5-24.5 inch (55.9-62.5 cm) tall at the withers and weigh 65–80 lb (30–36 kg). Females should stand 21.5–23.5 inch (54.5–60 cm) and weigh 55–70 lb (25–32 kg). By comparison under UK Kennel Club standards, height should be 22–22.5 inch (55.9–57.2 cm) for males, and 21.5–22 inch (54.6–55.9 cm) for bitches.
Coat: The Lab's coat should be short and dense, but not wiry. The coat is described as 'water-resistant' or more accurately 'water-repellent' so that the dog does not get cold when taking to water in the winter. That means the dog naturally has a slightly dry, oily coat. Acceptable colours are chocolate, black, and yellow. There is much variance within yellow Labs. Colours should be solid, though varying shades of yellow on the same dog are acceptable in yellow labs. A small white spot on the chest on black labs is the only acceptable variance from a solid colored coat, but it is not ideal.
Head: The head should be broad with a pronounced stop and slightly pronounced brow. The eyes should be kind and expressive. Appropriate eye colours are brown and hazel. The lining around the eyes should be black. The ears should hang close to the head and are set slightly above the eyes.
Jaws: The jaws should be strong and powerful. The muzzle should be of medium length, and should not be too tapered. The jawls should hang slightly and curve gracefully back.
Body: The body should be strong and muscular with a level top line.

Chocolate Labrador
The tail and coat are designated "distinctive [or distinguishing] features" of the Labrador by both the Kennel Club and AKC. The AKC adds that "true Labrador Retriever temperament is as much a hallmark of the breed as the 'otter' tail.
http://en.wikipedia.org/wiki/Labrador_dog