The AKM was designed in the 50s as an update to the venerable AK-47. It was used in the Soviet Army and has also been copied in many other countries. The AKM is the most common design that you will see today. The AKM uses the same 7.62x39mm cartridge that the AK-47 uses. The AKM is select fire capable of either semi-automatic or full automatic fire.
The main difference between the AK-47 and the AKM are that the AKM has a stamped receiver as opposed to the milled receiver of the AK-47,. The AKM also used lighter weight parts and was reportedly more stable during full automatic fire than the AK-47.