How is defined ('_JEXEC') or die ('Restricted Access')?

Question

This line is at the top of the templates and modules:

defined('_JEXEC') or die('Restricted access');

And from Joomla! Documentation :

This statement checks if a file is being called from Joomla! and protects your site, making it more difficult for a cracker / hacker to damage your site.

_JEXECdefined in a file index.phpin the root directory of Joomla! [source] site , which will prevent someone from identifying _JEXECon their own site and turning on my module, since it defined('_JEXEC')returns true?

Answer 1

, , _JEXEC . - , , -, /index.php.

- _JEXEC

. php , , , , php-, ?

Answer 2

- Joomla . , .