FQN acronym stands for Fully Qualified Name, and is the full path to a file in the repository. FQNs are case-insensitive, and are used when referencing art repository assets by the server or client engines.
One place that FQNs are used, is in the Area Asset Class on the server side. The nodes of that class store the FQN that references the art to be displayed when that asset is instantiated.
A GUI referencing a texture:
<_panel name='buttonImage' texture="GUI\_CleanEngineGUI.dds" ignoreMouseEvents='true'> </_panel>
Examples of paths