Most of time index files (index.php, index.html, etc) are used to disable directory listing, it’s a simple empty file with index as name. Every subfolder need to have this to not allow directory listing.
If index.php is the main file with the web info that’s means that you call sub folders instead of files and you are not able to have more files inside the same folder at least that you explicity call it directly with all the path ending with the extension (/login/login.php).
File .htaccess works in conjuntion with php files, you can write rules (RewriteRule) to point to specific file into a folder as @ben correctly says and show empty index.php with DirectoryIndex , e.g.,
root/index.php
root/login/login.php
root/help/help.php
The great about this is that Wappler create that routes for you inside .htaccess, so you only have to worry about to create routes inside Wappler.
With Wappler routing you can have something like this without writing extension at end, that’s call URL rewriting. More info here: About the Routing and URL Rewrite category
/login
/help
/about
/about/offices
/services
/services/portfolio
/services/clients
etc, etc.
Routing example with the real path could be:
/login/login.php ----> /login
/about/about.php -----> /about
/about/offices.php -----> /about/offices
Sorry if made some mistake, I’m writing this rapidly.