The layout administration is the place to manage all installed Layouts.
Please note: Other words for "Layout" are "Template" or "Theme"! What is called "Layout" in Bigace might be called different in other software products (there is no standard wording for it).
The Layout administration is the place to:
See which Layouts are installed
Check the currently configured default Layout
Check metadata (like path and extended options) of Layouts
Edit the Layouts sourcecode
Links for Designer & Developer:
If you want to customize a Layout, the following articles might help: