Google Docs is very popular on the internet because it offers Online Document, Spread sheet, Slider with plenty of amazing tools and also its upgrading the feature that people can collaborate to see the changes instantly without refreshing the page.
If you remember, Google Docs was initiated with the following URL docs. google.com or google.com/docs but after introducing the Google Drive, its changed Google docs URL to Google drive as redirection without any information of redirecting and from the Google drive page you can access to the old docs and create new docs.
Now if you visit Google docs docs. google.com or google.com/docs, then you will see a message that Google is bringing back the google docs to google documnets page itself.
Separate URL's for Google services
Related to Google Drive