A more thorough explanation:

The National Firearms Act is a federal law that was passed in 1934. It regulates the manufacture, possession, and transfer of certain types of firearms and other weapons.

The original purpose of the act was to ban weapons commonly used by gangsters, such as machine guns and sawn-off shotguns. Over time, the act has been expanded to cover most rifles and handguns, as well as "destructive devices" like grenades and land mines.

For example, if someone wants to own a machine gun or a grenade, they must comply with the National Firearms Act. This means they must register the weapon with the government, pay a tax, and undergo a background check.

The National Firearms Act is important because it helps to keep dangerous weapons out of the hands of criminals and other people who should not have them. It also helps to ensure that people who do own these types of weapons are responsible and law-abiding.