Often described as a son of Aphrodite by her lover Ares, the god of war, Eros was a Greek god of lust and primal sexual desire. In fact, the word erotic comes from his name. He is personified in all kinds of love and lust -- heterosexual and homosexual -- and was worshipped at the center of a fertility cult that honored both Eros and Aphrodite together.
There does seem to be some question about Eros' parentage. In later Greek myth he is indicated to be Aphrodite's son, but Hesiod portrays him as merely her servant or attendant. Some stories say Eros is the child of Iris and Zephyrus, and early sources, such as Aristophanes, say he is the offspring of Nix and Erebus, which would make him quite an old god indeed.
During the classical Roman period, Eros evolved into Cupid, and became portrayed as the chubby cherub that still remains as a popular image today. He is typically shown blindfolded -- because, after all, love is blind -- and carrying a bow, with which he shot arrows at his intended targets. As Cupid, he is often invoked as a god of pure love during Valentine's Day, but in his original form, Eros was mostly about lust and passion.