Google Drive is a web-based file synchronization service launched by Google on 24-April-2012. It replaced Google Docs and provides 15 GB of free storage (shared amongst Gmail, Google Drive, and Google+ Photos), with the option to rent more.
Questions here on Android Enthusiasts should be concerned with the Android app.
There are Mac, Windows, and iOS (iPhone/iPad) clients that allow for automatic synchronization to/from local storage (similar to Dropbox) as well as a web interface.
For questions specific to...
- the Web app, please visit Web Applications.
- the computer client, please visit Super User.
- the iOS app, please visit Ask Different. (May also be appropriate for the Mac client.)