The Google Docs suite -- including Drive, Docs, Sheets, and Slides -- is a free, easy-to-use, and surprisingly rich collection of productivity software tools.
Free: Like Google's other consumer services, the Google Docs collection of cloud-based productivity apps, which Google refers to as "Docs Editors," are free to use.
Work in the cloud: All your documents are kept in Google Drive cloud storage. Out of the gate, you get 15GB of storage for free. You can purchase 100GB for $19.99 per year or 1TB for $99.99 per year. Your Gmail messages and Google Photos can count toward your storage cap. By default, you need to be connected to the cloud to work on files, but you can install a Google Docs offline extension and turn on offline access to work when not connected.
Easy collaboration: Share a text file, spreadsheet, or presentation by tapping the Share button and adding people by name or email address. Set whether colleagues can edit, comment, or just view the file and if they can download, print, or copy the document. Collaborators can add comments to a file and address comments made by others. You can view collaborator edits in real time and chat with others working on a file in a message window.
Word processing: Docs, the word-processor app, lets you create, edit, and format text documents. You get text and paragraph formatting tools and can add links, images, and tables; view an outline of your document; run a spell checker; and see word and character count.
Spreadsheets: With the Sheets app, create, edit, and format spreadsheets. You can also build charts and graphs and use built-in formulas. Based on the data in a spreadsheet, Sheets can suggest chart types and analysis through its Explore tool.
Slides: Slides is Google's presentation app. You can build slides, create transitions, and work with text, shapes, and tables. As a bonus, you can drive your presentation from your phone, presenting via Chromecast to a monitor or through a Google Hangouts video chat.
Companion apps: Google offers a collection of related productivity apps to support Docs, Sheets, and Slides: Keep for taking notes, Drawings for charts and diagrams, Forms for survey and forms, and Sites for creating Web pages.
Compatible with Office files: You can import Microsoft Office files -- including Excel data sets -- and convert to Google Docs files. With Office Compatibility Mode (OCM), you can work on Office files in their native formats, and you can save and export files in an Office format.
Templates: Google offers 70-something text, spreadsheet, and presentation templates -- from a project proposal to a to-do list -- to give your documents a polished look.
Add-ons: Through third-party add-ons, extend the functionality of Docs, Sheets, and Forms. Add-ons range from charting tools to bibliography creators and cluster around business and education uses. You can also add custom items, such as menus and dialogs to Docs, Sheets, and Forms with Google's Apps Script.
Lacks premium features: The Google Drive apps lack some high-end capabilities you can find in a paid productivity suite like Microsoft Office. For industrial-strength capabilities, other tools might be more appropriate.
Unless you are looking for productivity apps to perform some heavy lifting, Google's free and collaborative Drive, Docs, Sheets, and Slides apps should be more than up to the task.