With the 1.10 patch Blizzard has integrated a new content delivery system called the Blizzard Background Downloader. This program will run seamlessly with World of Warcraft and download upcoming content prior to the release of a patch. With use of this program a minimal amount of data will be needed during the next actual patch release and help to decrease the amount of time spent downloading the patch. The Blizzard Background Downloader uses the same protocols and connection methods as the Blizzard Downloader, some customers may need to configure their various network protection programs and hardware to take full advantage of it.
Additional information can be found on our Technical Support site here