Currently, there was no globally adopted standard when it came to differentiating between different breeds of dogs. If we followed the American Kennel Club's standards, pet dogs would generally be categorized into seven different groups: sporting dogs, hound dogs, working dogs, terriers, toy dogs, herding dogs, and non-sportings. These categories were formed in order to make competitions easier to handle, but dogs were generally split into two types: working dogs and non-working dogs.
Working dogs were dogs that were able to assist humans in their daily life or work. The others fell into the non-working category. Most of them were small breeds, like Pekingese, Chihuahuas, and Pomeranians. Other than accompanying humans and providing joy, they didn't have much use.
Simply put, what working dogs could do, non-working dogs couldn't. But what non-working dogs could do, working dogs could, too.