In addition to the standard diagonal screen of 7 inches, this device highlights the unique capability - support for 3D content. The new tablet will reportedly be developed as part of the project Tango, so it will have two cameras that will be able to record 3D video and photos. Tablet with advanced recording should, according to the same source, be presented to the public just before Google's annual developer conference in June.
Google previously released Tango smartphone which was mostly used for building virtual 3D maps of rooms with 3D scanning. If you missed the article about the Project Tango feel free to remind yourself here.