The .htaccess file is a configuration file of the apache server. Through the file in the APPNET OS root directory, all requests are redirected to the index.php file.
This is important because all requests are processed via the index.php.

If you use a web server other than apache for APPNET OS, you must configure the configuration file of the relevant server, otherwise APPNET OS cannot run.

If not already configured globally, you should absolutely prevent access to the document directory.