You could do word processing and number crunching with Google Docs a long time ago, and then they were all integrated with Google Drive, and now - with support for offline processing and syncing - they are becoming "standalone mobile apps" in Google's terms...
Brian Levee, Google Product Manager writes:
Every year, phones and tablets get better, and more of you are starting to use your mobile devices not just to view, but also to create and edit content. And while the Drive app is a convenient place to store your stuff, we want to make it easier for you to quickly find, edit and create documents, spreadsheets, and presentations on the go. Starting today, you can download new, standalone mobile apps for Docs and Sheets—with Slides coming soon. Need to find a spreadsheet? Go to the Sheets app. Need to create a document? Go to the Docs app. They’re all right there at your fingertips.
See also: How to use Google Maps offline mode on iOS, Android [CNet]