Different guns

Kalashnikov
A type of rifle or sub-machine gun made in Russia
The inventor is Mikhail Kalashinkov
There have been 100 million Kalashinkovs made
In Black Market there are Kalashinkov style guns for sale as little as $6
The short name for a Kalashnikov rifle is AK 47
The AK represents "Avtomat Kalashinkova", in Russian that means "Automatic Kalashnikov" and the 47 is because the gun was created in 1947


AR-15
The AR-15 is lightweight, American rifle which comes in fully automatic or a semi-automatic gun
The AR is AR-15 stands for ArmaLite Rifle