Google Drive is Google's free online file storage system and where Google Docs reside. It's web based, has Mac and Windows apps and mobile apps for iOS and Android. I love it. I have Google Docs on there, but also have other files uploaded there for easy access and use anywhere.
Google Drive for Android has let you view, create and edit Google Docs for a while. iOS users now have reason to rejoice, as you can now edit and create new Google Documents on your iPhone or iPad. You can also view Google Presentations on your iOS device as well as create new folders and move files into folders and upload files right in the app. This is great news for iOS users.
The Android app also got an update. It has had edit, create and view for Docs for a while, but now lets you add comments, reply to comments and view tables in Docs, as well as view Presentations and organize folders and upload files.
Source: Official Google Blog
Android App: Google Drive in the Play Store
iOS App: Google Drive in the App Store
Here's a video from Google about Google Drive for Mobile.