The AKM was designed as an improvement over the AK-47, and served the Soviet army from 1959 until the adoption of the AK-74 in the 1970s. The AKM features a number of upgrades over the AK-47 to make it even more suitable for widespread adoption.
To this end, the AKM features a steel stamped receiver over the milled steel receiver of the original AK-47, overall simplified manufacturing methods, an enhanced barrel for superior accuracy, and a reduced weight.
Most of the changes from the AK-47 to the AKM are internal, and when looking at the rifles from the outside they are virtually identical. Most people who see the two rifles together cannot tell them apart.