The iconic Cupid with his baby-fat hands clenching his bow and or arrows is all too familiar from Valentine's Day cards. Even during the Classical period, as you can see from the accompanying picture, people recognized this sometimes mischievous precocious ancient baby, but this is quite a step down from his original exalted heights. Originally, Cupid was known as Eros (love). Eros was a primordial being, thought to have arisen out of Chaos, along with Tartarus (the Underworld) and Gaia, the Earth. Later Eros became associated with the love goddess Aphrodite, often as her son Cupid, most notably, in the myth of Cupid and Psyche.
Cupid shoots his arrows into humans and immortals alike causing them to fall in love or hate. One of Cupid's immortal victims was Apollo.
Psyche is the Greek word for soul. Psyche's introduction to mythology is late, and she wasn't a goddess of the soul until late in life, or rather, when she was made immortal after her death. Psyche, not as the word for soul, but as the divine mother of Pleasure (Hedone) and wife of Cupid is known from the 2nd century A.D.
You can't always pin down the author of a myth, especially one that shares so many elements with Beauty and the Beast and other fairy tales of its ilk, but the version of the myth of Cupid and Psyche that we have comes from an early, risqué novel by an African Roman of the 2nd century A.D. His name was Lucius Apuleius. He comes up elsewhere in history because he was charged with practicing witchcraft. His novel is thought to give us inside details of the workings of ancient mystery rites, as well as this charming romantic story of love between a mortal and a god.
Apuleius' novel is called either Metamorphoses/Transformations or The Golden Ass/Asse. In its main story, Lucius is transformed into a donkey. The myth of the love story between and marriage of Cupid and Psyche is embedded and comes from Books 4-6.
Apuleius is only one of the authors of a Metamorphoses/Transformations. In the relatively modern world, Kafka wrote a Metamorphoses and before Apuleius' time, so did Ovid.
In connection with what was said in the paragraph about Cupid, in Ovid's Metamorphoses, Cupid's arrows caused Apollo to lust after Daphne and Daphne to hate Apollo, with the end result that she was transformed into a tree.