A common sight in Angkor temples. What is it? It's a lingam on a yoni. What's that, you ask? It's a sacred representation of the infinity of Shiva, the primary deity in most Angkor temple prior to the conversion of the Khmers into Mahayana then Theravada Buddhism. You want a simpler explanation?
It's a cock (lingam) penetrating a vagina (yoni).