I can see
Work with Google Drive
sentence in websites and web apps. What we can do with integrating our websites with Google Drive?
Is it similar to things with other services like Dropbox and Ubuntu one?
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Sign up to join this communityThere were many details about creating and using apps with Google Drive. There was less about the services you mentioned, which kind of surprised me.
I found a section that described a Dropbox-like functionality for visitors to use on your websites. To understand it, read through Google Drive Apps Overview first. You'll see the Picker description (toward the end of that webpage), which is how users can select from a menu that looks a lot like Google docs.
Summary: The docs are stored on Google Drive, and one selects them using Picker. That was how I understood it, I haven't tried to implement it yet!