This is a special configuration for this short case. Per default the space with the space key IDX is the default index space. For the show case we insist that the show case index space is the root space. Therefor this property is set to false.
This space property controls the rendering of short descriptions. If set to true, the short description will be rendered above the metadata. If unset (or set to false) the short description will be rendered as part of the table like all other properties (which happen to have non-blank value and that have not a control named hide).
A second space property that controls the visual representation of metadata on a page. The value definition-list instruct projectdoc to render all metadata table as definition lists. In the screenshot above you can see the property Relation with value projectdoc being rendered as a one element definition list.