The Shetland Sheepdog (or Sheltie) is a breed of dog, originally bred to be sheep dogs. It resembles a miniature Rough Collie; as a breed, however, it is unrelated to the Collie, but is instead a cross between the Norwegian Buhund and the Icelandic sheepdog.
Shelties are known for their loyalty and obedience to their masters. They are friendly and affectionate, but reserved around strangers. In their size group, the breed dominates dog agility competitions.
Several coat colors exist. The best-known are the sable and white (golden-tan with white underneath) and tricolor (black on top, white underneath, with tan between), although blue merle, red merle, and other colors are acceptable.
Courtesy of: The Free Dictionary