If you have kids in your home, you have probably worried about them suffering electrical shock from sticking items into your wall outlets. Some try to prevent this by inserting plastic coverings into the outlets, but those can be removed by an insistent child, or you might forget re-inserting them when removed.
A safer alternative is a tamper resistant outlet. You can identify these outlets by the letters TR imprinted on the surface of the receptacle.
These outlets are designed in a way so that they won’t allow an item to be inserted into only one hole, but instead they require a double-prong. This is achieved by a spring-loaded shutter mechanism. When both prongs push against the shutters there is enough force for it to open and allow a connection. The shutter will close again when you remove the plug.
While tamper resistant outlets are slightly more expensive than regular outlets, it is a worthwhile investment for keeping your children safe.