what can the UDL be used for?
Viewing post in CopperCube++ to Notepad++ UDL file
Without sounding rude, I'm not sure why the description and instructions don't easily explain that to you?
It's a UDL file for use with Notepad++ as the title states. It won't be any use to anyone who does not code scripts.
If you don't know what either are then search google as it's a very popular script editor.