Noon Pacific is currently on sale in the Play Store (also, hey, they changed the layout in the Play Store!) for $0.99. This is down from its usual $3.99 price point. I believe the app is also on sale on the App Store. (Just got an email about this from Noon Pacific, which is why I'm aware of the sale.)
As to what the app does, well here's another screenshot!
For more screenshots check out the Play Store listing.
The long and short of it though is that every Monday at noon pacific (hence the name) they put out a new playlist of music that's more often than not worth checking out. They also put out special (and incredibly lengthy) playlist a few times a year.
Side note: If you're an 8tracks user or even if you're not you can just visit Noon Pacific's page in your browser and check it out that way.
Additional side note: If you use Infinitracks, which I personally do because it's better than the official 8tracks app, you can basically skip on this entirely. (Although it's worth owning in and of itself, the Infinitracks app that is. Definitely pay for the extra features, they can be a bit pricey but they're more than worth it. One such feature is Chromecast support, I love randomly leaving a good 8tracks playlist playing on my setup at home at night and passing out while listening to it.)