How to understand an entry in htaccess?

Question

htaccess

Actually, there is such a record, help me understand what is happening in it?

RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*)$ index.php [QSA,L]

Answer 1

RewriteCond %{REQUEST_FILENAME}- if this file
-d- is a directory
Not a ! negation
in the sum if it is not a directory
RewriteCond %{REQUEST_FILENAME} ! -f- respectively, if it is not a file
RewriteCond +RewriteCond+RewriteCond and so on until the RewriteRule appears
and consequently the first two rules are formed.
then Redirect everything (.*)to index.php keeping GETQSA