20 global- + 12 local-view layers in Blender??

The2.5 Manual has a page about the Python Text Editor with a very nice video-tutorial. They say there that blender has 20 global- and 12 local-layers.

Up to now I only knew about 20 layers. And cannot find these new 12 ones. The terms global and local are also strangers to me. Although I see the words mentioned in the Transform Orientations-list on the footer of the 3D-view I have as for now no idea what they mean…

Please don’t critisize me for not adding any link: the site simply doesn’t accept a single one! Hope you find what I am talking about. If not a similar post, including links, is on the BlenderNewbies Forum.