Introduction to the Cloud - Beginning iOS Cloud and Database Development - page 15

Figure 2-1. The three core functions of the iCloud API
When the user makes alterations to a document on his device, iCloud notices each of the changes
and makes updates to the documents that have not yet been changed on other devices. iCloud only
sends out the differences in the document, which then become versions of the original. There is
virtually no labor necessary on the part of the user. The application handles the issue of sending the
files up to iCloud. This process actually involves breaking down the document into several smaller
pieces of data, called “chunks” or “pieces,” and then pinpointing the data that has been changed.
These chunks are then sent to all the devices connected the user's Apple ID. This then becomes
version two of the document.
The place where you store files that you want to sync to iCloud is called the Ubiquity Container.
The Ubiquity Container serves as a master file and is designated as the vehicle that passes your
documented data between your devices and iCloud (see Figure 2-2 ).