The HY-1 and HY-2 Hai Ying (Pinyin: ha(iyi-ng; literally "Sea Eagle") are the "Silkworm" missiles.
HY-2 is the anti-ship cruise missile made by China based on the Russian SS-N-2 Styx missile.
Silkworm refers to both HY-1 and HY-2 missiles.
HY-1 missile = NATO codename CSS-C-2.
HY-2 missile = NATO codename CSS-C-3