For a few years now Google Docs users have been able to sync their accounts for offline use. Over the last few years offline access has been added for Slides and Sheets too. All that said, the process for enabling offline access was a bit tricky for some users (directions are available here). Fortunately, Google has just announced that using Docs, Slides, and Sheets offline is about to become a lot easier.
Over the next couple of weeks offline access will become the default setting for folks who sign into Chrome on the web and visit Drive, Docs, Sheets, or Slides. Bear in mind that you have to sign into Chrome. If you’re using a public or shared computer, you probably don’t want to sign into Chrome on that computer so that you can avoid accidentally granting access to your Docs, Slides, or Spreadsheets.
Google Apps for Education users should note that their domain administrators can still disable offline access from the domain administration panel.