It's a rhythm game. The presentation is really impressive but it's mostly geared toward young girls. As you play you watch your character and the person you're competing against dance. The characters are 3D and cel shaded.
There's also a photo mode where you can take pictures of your character. She just keeps posing and you can rotate her and snap as many shots as you want.
You earn points from the dancing part and you can buy clothes and hair styles for your character.
haha! When you're changing her clothes in the shop, if it doesn't load the new clothes fast enough you get a quick look at her in her panties.