Sadly, the service will be limited to US only for the initial period and there is no information on when it will be rolled out to other countries. Google Music is a service which gives you access to your personal music collection without the need to use wires or sync. You can add your music collection to Google music and access it from the web or any other compatible Android device.
If you are interested in trying out the new service, you can request a beta invite for the service by visiting http://music.google.com. You can learn more about Google Music by visiting this page.