Apple's iWork for iCloud is an online suite similar to Microsoft Office Online or Google Apps.
This cloud-based version of Pages, Numbers, and Keynote was originally restricted to owners of an Apple device such as a Mac, iPhone, or iPad. As of early 2015, users across myriad platforms now have the option to create an iCloud account which grants access to the productivity apps.
How to Get Started
The iWork for iCloud suite is free, though you do need to sign up for an account.
Online Storage Included
Signing up for iCloud gets you 1 GB of free online storage, which will be helpful since iWork for iCloud is a completely online suite.
The implication is that you will need to have a reliable internet connection in order to work with documents stored in iCloud or this version of Pages, Numbers, and Keynote.
Official System Requirements
Of course, Apple still recommends their desktop and mobile devices above other platforms. But the company does list specifics for more than their own devices on their official iCloud System Requirements page.
I recommend visiting this page no matter what device you are using iWork or iCloud on. It includes a table with operating system version requirements for several individual features including:
- Mail and Mail Drop
- Family Sharing
- Find My Friends
- iCloud Photo Sharing and My Photo Stream
- Reading List
- Two-step Verification
In summary, this system requirements chart shows how many iCloud features other than iWork are only available to Apple device owners.
Check out this in-depth review: Top Features in iWork for iCloud.