A remote training dog collar, also called an ecollar is a tool to teach your dog from a distance. The remote training collar consists of the dog collar and a separate hand held remote. There are settings on the remote to allow the trainer to adjust the intensity. Most remote collars also have a tone only mode, that simply sounds a tone to let the dog know that the behavior is unwanted.
The collar with the transmitter has two probes that deliver the "tap" to the dog's neck. The collar has to be quite snug to be effective, usually allowing on one finger to be inserted between the dog's neck and the collar. Always start on the lowest level. Continue to use the lowest level necessary to get the desired behavior.
There are different methods of ecollar training. One method is called the avoidance method - this method involves holding down on the button until the dog completes the desired task. In this way the dog will do the desired task as quick as possible until you get to the point that the dog will "beat" the button.
Another method is to simply "tap" the button when the dog is doing an undesirable action. A quick tap is given and additional taps at increasing intensities until the dog stops the behavior.
There seems to be much debate about training your dog with a remote collar. Many have used this method with great success. Others call it cruel, however, I have rarely heard anyone call the invisible fence pet containment system cruel. I wonder why people don't make the connection that they are the same thing.
E-collars are definitely getting more popular among the general dog owning public, because they can produce such a high level of obedience in such a short amount of time.
One thing to remember is that these collars are a very effective training device and are usually only necessary during the training process. Once the dog is trained, the collars are rarely used.