A shock collar is a device used to train or control dogs through the use of an electric stimulus. The collar has two prongs that touch the dog's neck, and when activated by the owner, it delivers a small electrical shock to the dog as a form of negative reinforcement.
The idea behind using a shock collar is to create an association between a specific behavior (such as barking or running away) and an unpleasant sensation that will deter the dog from repeating that behavior in the future. However, many animal welfare organizations argue against their use due to concerns about potential harm to the dogs and questions about their effectiveness over the long term.