There are now two recongnised breeds, namely the Parson Russell terrier and the Jack Russell terrier. To understand the similarities and differences of the two breeds we need to go back to their origins.

Origins of the Terrier

Terriers are thought to have descended from small hunting dogs that the Romans brought to Great Britain. They've been used for hunting since time immemorial. They were first used to fight vermin and also learned to go underground (TERRA is the Latin word for earth).
Although most people associate terriers with England, they were actually first documented in France.

Terriers only became common in Britain in the sixteenth century. While they were first bred as hunting dogs, breeders later to breed dogs in certain quarry. Some terriers were masters at tracking down and hunting rats and mice. Others were specially trained to hunt weasels and otters. By this process of selection for certain traits, various varieties of terriers developed over time. The Jack Russell descended from the fox terrier types and was originally bred to hunt foxes.

It was a parson, the Reverend John Russell (1795-1883), who gave this breed its current form. He needed a dog that could work well underground. In 1819 he bought a terrier bitch, 'Trump', and she was the first in a long series of dogs that Russell used to create what he thought was the ideal working dog. Only towards the end of his life, did the terrier as we know it today come about. 'Jack' of course is a dimunitive of 'John', hence the names Jack Russell and Parson Russell. Over the course of time three different types have developed from that breed.

The Wire-haired Fox Terrier

This breed was recognised in Britain in 1913.

The Working or Hunting Parson Russell Terrier

Young dogs that seem particularly suited for hunting were selected for further breeding. Generally these dogs stand somewhat taller.

The Family pet Jack Russell Terrier

Dogs that didn't make the high standards for hunting dogs were sold as family pets.

In many cases the bloodlines of the three varieties continued to cross, but over time the three breeds differed more and more from each other. Jack Russell terrier clubs were formed, especially in Britain and the US. However, there was absolutely no sign of harmonisation or official recognition. This was only changed in recent times. The Kennel Club of Great Britain recognised the breed on 22nd January 1990 and published an official, provisional, standard under the name Parson Jack Russell terrier. A few months later the breed was accepted by the FCI (the umbrella organisation for Western European kennel clubs).