It’s pretty much the music service you would expect from Google: Streaming all your songs from the cloud, once you’ve uploaded your own music, and a bit of offline playing too.
How do you use it? You use Google’s Music Manager on your desktop to add your songs to the service. It adds play counts and ratings as well. It has all the features of an offline music player like iTunes making it the all-round music experience.
The songs are automatically added to all your Android devices also and you can stream music from them too. So all your devices: Phone, Tablet, Computer have the same music library and wastes no space in your device at all. You can add music to be played offline(that will take memory though)
To make it easy to add and manage your music you can directly import songs from famous music players like iTunes, Windows Media Player etc. You can request an invitation if you live in the USA by clicking here