The concept, based on works of fiction, is that your gun is somehow set so that it will only function if you're holding it. Thus, children can't use it. Criminals shouldn't bother stealing it.
The concept is, if all gun owners are required to have a huge insurance policy that will pay for injuries, deaths, property loss, etc, resulting from their guns being used in a crime (whether or not it's by the gun owner) the cost to society will be lessened.