All the major kennel clubs of the world classify purebred dogs into a number of different categories, or groups; both the names of these groups and the criteria for inclusion may vary from kennel club to kennel club. Indeed, there are a number of cases where one country includes a particular breed in a certain group, while another country includes that breed in a completely different group. What's more, the types and even descriptions of the various groups can differ between kennel clubs, even kennel clubs found within the same country! Given all this divergence, it's no wonder that there sometimes exists confusion as to how exactly classify a particular breed of dog. The Silky Terrier is an example of this confusion. Its name clearly states that there is something "terrier" about it, though many kennel clubs, including the AKC and Britain's Kennel Club classify it in the Toy group. Not everyone is in complete agreement with this classification, though; in America, the Continental Kennel Club classifies the breed in the Terrier group. So which is it? And what's the difference between a toy and a terrier?
A terrier is a type of dog that was developed for the specific purpose of hunting and killing vermin, or small game, such as rabbits, badgers and foxes; terriers were especially used as ratters, or for killing rats. At times, they were used in conjunction with other dogs on hunts. Terriers are small dogs (though there are one or two that are a bit larger), as they needed to be able to chase small vermin into burrows or holes and they are very, very tough and energetic; rats could be very brutal and ratting dogs needed to have the courage and energy to confront them. Today, the ratting function of terriers has become somewhat obsolete (though it hasn't disappeared altogether) and most terriers are kept as companion dogs.
A Toy dog, on the other hand, is a bit more difficult to identify; most dog fanciers agree that, essentially, a toy dog is a small dog whose main purpose is to be kept as a pet. Beyond this, though, there are some contrasting ideas as to what constitutes a toy dog. Some believe that toy dogs should be classic "lap dogs", with no real need to exercise; others disagree entirely and claim that some toy breeds are quite rambunctious. Some claim that toy dog breeds must have been developed SOLELY as companion animals and must never have been used to perform any other function; again, others disagree and allow for the inclusion into the toy group of breeds that once had other jobs, or that today can be used for purposes other than companionship.
Silky Terriers are today mainly considered true "toy terriers"; they are small dogs, which are kept as companions and which were most likely mainly bred for companionship. They are not, however, "lap dogs" and retain that hyperactive, energetic, tough terrier personality. Furthermore, in conformation shows of kennels that consider this breed a toy, judges must look for a certain substance in the Silky Terrier's structure that attests to the fact that they could be used in the classic terrier function of hunting vermin. Indeed, many sources claim that the original Silky Terriers were used as ratters.