Basically this all boils down to semantics.
Technically, the AK-47 was a select fire assault rifle used by the Soviets from 1947-1959. It featured a milled steel receiver, and was replaced with a slightly updated version called the AKM that featured a stamped steel receiver at the end of the 1950's. In the 1970's, it was further modernized and chambered for the new 5.45x39mm cartridge and given the designation AK-74.
However, in today's terminology, AK-47 usually refers to any AK pattern rifle chambered in the original 7.62x39mm cartridge. Likewise, AK-74 typically refers to AK variants in 5.45x39mm. There are transferable select fire versions out there, but the vast majority are semi auto.