If "-f %{REQUEST_FILENAME}" what mean's - fcgi

I configures my apache + php-fpm + mod_proxy_fcgi server and I can't understand the line in the two tutorials that don't explain why. This is not found in any other tutorial. SetHandler "proxy:unix:/run/php-fpm/example.com.sock|fcgi://example.com/" -------- I don't understand line: I was able to determine that this line means: 'check if the file really exists' I understand correctly? If so, why check? maybe it's not needed?