I think the first letter in the commonly used German cable designations refers to the outer sheath (i. e. either N for non-metallic or nothing at all), the following letters offer a further descriptions. YM is conduit wire, NYM is the very same stuff with an outer sheath, NYIF is the famous "zip Romex". YE is conduit grounding wire. For flexible cords most people seem to use the international designations, but here in Austria there's one exception. YZWL is zip cord. (ZWL standing for Zwillingsleitung, twin cord). That's about all I know about those designations. Yeah, and a suffix -J or -O refers to with or without grounding conductor.
