Many people who see a rifle that looks like an AK-47 assume that it’s automatically called an AK-47. But the truth is that the only true AK-47 is the original AK-pattern rifle that was released in the year 1947. There have been many, many variants of the AK-47 made since then in a wide variety of configurations and calibers, but they all have different model names (such as the AK-12 or the AKM or the AK-74 and so on).
The original AK-47 was the brain child of Mikhail Kalashnikov. During World War II, the Germans had fielded the first true assault rifle, called the STG44. By definition, an assault rifle is any rifle or carbine that fires an intermediate round and has selective fire capabilities. In an era where slow-firing bolt action rifles were the norm as infantry weapons, the STG44 gave the German soldiers issued it a major advantage on the battlefield.
The Soviet Union captured several STG44s during the war and were impressed the weapon, and immediately set out to design a similar rifle that would replace the aging Mosin Nagant bolt action rifles, which had been in service in the 1890s. Kalashnikov submitted the winning design in the form of the AK-47, and over one hundred million were built. Chambered for 7.62x39mm, which has ballistics very similar to the .30-30 Winchester, the AK-47 served as the basis for the AK-pattern rifles, which are the most widely distributed firearms in history.