The Google decided to unify the services of the Android Market, Google Music and Google eBookStore, transforming the old store into something bigger and better: The Google Play Store, the new Google's store has new layout and new address.
The new store includes applications for Android, Google Music songs and Google eBookstore books. Therefore, any purchased content on Google Play serves to smartphones, tablets and PCs.
The Google Play Store is born with more than 450.000 applications, more than 8 million songs and with the largest book's gallery on the planet.
What happens to your device?
Probably in a few days Google will make an update to the Android Market application, ie, its Android Market will get a new icon and replaced by a new name: Google Play Store. Applications will be available to other services that were added, such as Google Play Music, Google Play Movies and Google Play Books.
The applications already installed on your device will not impact and it will work normally.