Part of the importance of Aphrodite in Classical Mythology is her Birth (you can learn all of the important things about her on her own page, Aphrodite, so I'm not going to talk about them here - only tell her story).
When you think of Aphrodite, you probably think of the painting at the top of this page - Botticelli's beautiful white-skinned red-headed goddess sailing to shore on a shell. Well, shock me shock me, an artist finally got it right! Mostly. I mean, he got it as right as can be expected. The truth was, there was more than one story of her birth. The most well known has to do with her very name. Aphrodite means "out of foam." So without further ado, the story of Aphrodite's birth (according to Hesiod, a Homeric Hymn, and Pausanias).
Wayyyyyyyy back in the day, there was this dude named Uranus (Heaven). Now, Uranus wasn't such a great guy. He was totally harsh to his kids and his wife, so it wasn't much of a surprise when they turned on him. Gaia, his wife, sent their youngest son Cronus against his father, armed with a sickle. So, as Cronus was throwin' his dad out of heaven, he castrated him with the sickle (we are talking some serious bitterness towards daddy). The blood from Uranus' genitalia fell into the sea, and it was there that the beautiful Goddess of Love and Sex was born. She was blown to the island of Cythera by the sweet East Wind (possibly West or South, I don't actually remember) and as she arrived on the shore, she found the Seasons there waiting for her. They were dancing and singing her praises. They were very beautiful, but they were nothing compared to Aphrodite.
As she stepped off her pillow of foam onto the sand they clothed her in golden robes and jewels and led her to Mount Olympus. This leads to a whole other story - but we'll get back to that later.
The second most popular story is the one described and eluded to by Homer (in the Iliad), Apollodorus, and Euripides (in Helen). It says that Aphrodite is not so parentless as she seems, her mother's name is Dione. Her mother's name doesn't give to much information about her, it means "divine queen." So we must look to other myths for the answer to that. According to some Dione was a Titaness, according to others she was an Oceanid, she was also seen as the Goddess of the Oak, an earth goddess. Well, looks like we covered all the bases. So back to Aphrodite. Assuming that Dione was her mother, then her father was Zeus.
Don't worry, there's more! There are also stories that ascribe the parenthood of the Love Goddess to Uranus (the personification of Heaven) and Hemera (the personification of Day). And even another story that said that she was the daughter of Euonyme and Cronos. Euonyme may sound new to you. That's okay, she was new to me, too. Robert Bell says that she is an epithet of Gaia. So another Earth connection. But then Carl Kerenyi says that Euonyme is just a corruption of Eurynome (the Oceanid and Creatrix). I'm not sure which to go with. Try to believe all of them at once, if you can.
Okay, so back to the Seasons. Remember that they brought her to Olympus to meet the rest of the Gods? Well, the second she got there every God was on his feet. I mean, imagine Angelina Jolie (or Gwyneth Paltrow, whoever is more your style) stepping out of the shower and into your living room in seriously sheer lingerie, then multiply that feeling by 300 and realize that she isn't an actress and you aren't dreaming, rather she is a Love Goddess there to make your dreams come true. So it shouldn't be too much of a surprise that the Gods were all up (on their feet, that is). Each God really wanted to marry her - but in the interests of keeping things kosher in Heaven, Zeus gave her to the one God who didn't think he had a chance: Hephaestus, the ugly and crippled God of the Forge.
So Hephaestus was all thrilled. For, maybe, the first 3 minutes. Then he realized it might not be so great to have a Goddess who's only purpose in life was to love wildly and have gratuitous sex. I mean, that'd be great if she had a few of Hera's qualities thrown in, say, fidelity, for example. But I guess Aphrodite thought that would take too much fun out of it. She slept around on Hephaestus like no other. If you want to read more about this, then you should go to the Aphrodite page.