Terriers are natural diggers; the name comes from the Latin 'terra', meaning 'earth'. This is because they were bred and trained to catch vermin such as foxes, badgers and rats. Given their slippery prey, they tend to have a brave and persistent temperament, and plenty of energy in spite of their small size (perfect for fitting into a fox hole or badger sett). They need plenty of exercise, mental stimulation and training.
Not every dog that has 'terrier' in its breed name is in this group. For example, the Yorkshire Terrier is actually in the Toy dogs breed group, and the Boston Terrier is classed as a Utility dog.
Some examples of Terriers are listed below, or you can visit the Kennel Club's website for more information. Please also remember that every dog is an individual and both genetic and environmental factors affect their temperament.