If you are confused with the Google Play's complex interface and desire to know what this big thing Google is planning for future, then read the following FAQ I've compiled.
What is Google Play?
Google Play is entirely cloud-based so all your music, movies, books and apps are stored online, always available to you, and you never have to worry about losing them or moving them again.
What happened to Android market?
Android Market has been renamed to Google Play or you can say that it has been merged to Google Play.
Where will my purchased apps, music, movies, books go?
All those items will be stored in the cloud and won't eat up storage on your computer, tablet, or phone. When you purchase an app, movie, song, or book on the Play Web site, that content will become immediately available on your Android phone or tablet. If you rent a movie on your Android tablet, it becomes available for viewing on your desktop, too.
What are the Google services others than Android Market have been merged?
The Android Market will become "Play Store."
Google Music will become "Play Music."
Google Movies will become "Play Movies."
eBookstore will become "Play Books."
Can I upload my own movies and music?
Google Music, which allows you to store up to 20,000 songs, will remain the same. But Google does not allow you to upload your own movies for access in the cloud. Its Play Movies app solely functions as a movie rental service.
I don't have Android device. Can I use Google Play?
Yes, you can rent a movie, upload and purchase music, and buy books on one computer, and access it all on any other desktop. Even iOS support is coming in the near future.