* iTunes LP lets you create digital albums that include links to listen to album songs and view lyrics, liner notes, photos and videos (such as artist interviews).
* iTunes Extras is designed to present a movie with interactive menus, bonus content, and chapter navigation, similar to those supplied by DVD or Blu-ray authors.
Apple has also published information on testing and delivering the new formats.
Complete information on building content for the new formats is available at the Apple site.
Main story: http://www.apple.com/itunes/lp-and-extras/