The Jack Russell Terrier is a small terrier that has its origins in fox hunting; it is principally white-bodied and smooth, rough or broken-coated.It is commonly confused with the Parson Russell terrier (see the American Kennel Club) and the Russell terrier, which is a shorter-legged, stockier variety.he Jack Russell is an energetic breed that relies on a high level of exercise and stimulation and is relatively free from serious health complaints. Originating from dogs bred and used by Reverend John Russell in the early 19th century, it has similar origins to the modern Fox terrier.