Q: About "Clicker"
A: a mechanical device that makes a short, distinct "click" sound which tells the animal exactly when they're doing the right thing

Q: Clicker Trainig introduction
A: Clicker training is not someone’s new gimmick or special method. Clicker training is dog trainer’s slang for a positive reinforcement training system base on operant conditioning, a set of scientific principles describing the development of behavior in which the animal “operates” on the environment, instead of the other way around.
Operant conditioning goes to the root of how animals learn in the natural world; therefore the principles can be applied in any circumstance the possibilities for dog training are tremendous. Clicker trainers are developing ways to use this new technology with police patrol dogs; with service and haring dog; with puppies, even before weaning; for competition obedience and agility; n hunting, field trials and tracking; in the breed show ring; in “good manners” classes for pet owners; and in the home.

About Clicker Training
Clicker training does not really depend on the clicker or on food. Clicker training depends on rein forcers, which may be anything the dog likes (toys, petting, etc.) presented with a correctly timed signal in such a way that information is communicated between trainer and pet. We start with food as the reinforcer and the clicker as the signal because these are excellent teaching tools, for both you and your dog. Together you and the dog will be learning a new way of interacting.
Anything you need your dog to know can be taught by reinforcement training. After the dog has learned to understand what behavior you want, how to do it, and when to do it, you can replace the click with a word, and the food with a part; a word and a pat, you always have with you.
Once your dog acquires a clicker-trained behavior, unless you add new rules the dog will have that behavior for a life time. When the dog knows several behaviors, you no longer will need to click or to praise each one; you can reinforce once, for a whole repertoire. Eventually you’ll find that you get out your clicker only to sharpen up a response or to teach the dog something new – or just to have fun with your dog: clicker-training is fun for both of you.