Storing documents within the Cloud provides you with a common central location for easy access to those documents. Any updates that are made to the document can then be delivered to every iOS device or computer, as long as they are using the same Apple ID used to upload those documents.

When a document is uploaded to iCloud, it is not moved there immediately. The document must first be moved out of the application sandbox into a local system-managed directory, where it can be monitored by the iCloud service.

Once this process has completed, the file is transferred to iCloud and then distributed out to the user's other iOS devices as soon as possible. While the files are stored within iCloud storage, any changes that are made on one device are initially stored locally and then immediately pushed out to iCloud, using a local daemon service.

This is to prevent file conflicts from happening at the same time; this is handled by the File coordinator, which mediates...