try_files will handle checking if the file already exists, if it doesn't it will use ssi.html which will then handle including the file. If there isn't a reques

try_files will handle checking if the file already exists, if it doesn't it will use ssi.html which will then handle including the file. If there isn't a request for a specific file, e.g. https://example.com/ https://example.com/, then it will include "inc_index.html" (that's just the string "inc" not a variable "$inc" and I'm comparing to "/" from memory, it might just need to be an empty ""). You could skip the "set $inc $request_uri" line and simply use $uri (that's the normalized URI) in ssi.html.