iCloud Drive was officially launched alongside iOS 8 and is Apple's solution to managing documents across iPhone, iPad, and Mac. Users can subscribe to different tiered iCloud Drive storage plans based on their needs. iCloud Drive will then not only store documents and files from third party apps, but all of the other data iCloud itself has always been responsible for such as iCloud backups, Photo Stream, and more.
Up until iCloud Drive, all files were held in their respective apps. For instance, if you wanted to edit a photo in VSCO Cam and then in Snapseed, you would need to save that photo to your Camera Roll in order to then open it in another app. iCloud Drive should act as a better middleman between apps and allow access for any App Store apps that choose to take advantage of it. When choosing iCloud Drive as the source of your file, you'll see all the files you've saved to it, regardless of what app they were originally created in.
On the Mac side, iCloud Drive will integrate seamlessly just has Documents in the Cloud has done for a few years. For instance, if you start a spreadsheet in Numbers on your Mac, you can then pick up right where you left off on your iPhone or iPad, and vice versa.
iCloud Drive subscription plans range from free all the way up to $19.99 a month for 1TB of storage. Users can subscribe to an iCloud Drive plan on their iPhone or iPad by launching the Settings app and then choosing iCloud. If you find yourself running out of storage or not using all of it, you can choose to upgrade or downgrade anytime you'd like. iCloud Drive will be made publicly available with the launch of iOS 8 on September 17, 2014.