iTunes customers selecting movies, TV episodes and Season Passes, and completed seasons will now get the option to download the content immediately or to download it in the future through the iTunes in the Cloud feature. The new option also applies to music box sets and other music content which could take more time to download than a single track or album.
When a large purchase is made, a pop-up window will offer a user the option between "Later" or "Download." If "Later" is selected, the content is moved to the Purchased section, allowing customers to download at their leisure.
Apple's documentation (via Macworld) on the feature says that it requires an iOS device running iOS 6 or later or a Mac or PC running iTunes 11.
The option is available for users in countries where iTunes in the Cloud has support. A full listing of those countries is available on Apple's site.