The AR-15 is a semi-automatic rifle originally built by Armalite for the U.S. military in 1959. The design was purchased by weapons manufacturer Colt and became known as the M-16. In 1963, the Colt AR-15 became available to civilian customers. It is widely regarded as one of the most popular weapons available and is sold by dozens of different aftermarket gun manufacturers. In its most sought after configuration, the weapon is semi-automatic and fires the 5.56x45mm NATO round.
AR stands for ArmaLite Rifle.
Liberals seek to impose their will. They want laws banning weapons, this weapon in particular, despite the Constitution saying gun rights shall not be infringed. Being unsuccessful in this endeavor has not stopped Democrats from trying to impose their beliefs. Backdoor banning is the latest move. If they can't ban the gun, they will move on bullets. These methods include using the EPA to classify bullet casing as hazardous lead. California has such a law. Banning certain types of bullets that can pierce armor has made it to the U.S. House floor. Another is to dry up supply by having the government purchase billions of rounds of ammunition.