How do Plugins get their call-phrase?

[MortysTW]

vB3.5

I'm probably just struggling with using the proper terms with the search box, but I'm not having any luck finding this answer.

How exactly is it, that when you import an xml "plugin" to VB that it comes up with the "call-phrase" that it does.

Here's an example of a simple xml plugin file that I loaded to my site.

  <?xml version="1.0" encoding="ISO-8859-1" ?> 
- <plugins>
- <plugin active="1" product="vbulletin">
  <title>Photopost Feature Block</title> 
  <hookname>forumhome_start</hookname> 
- <phpcode>
- <![CDATA[ include('../gallery/inc_features.php');
  ]]> 
  </phpcode>
  </plugin>
  </plugins>

Now, this is the only file I added to my vB. Yet some how, it nows that when I put $photopost_features in my forumhome template, that it loads the proper php file.

Basically I guess I just need a clarification.

Since the hookname is forumhome_start does that mean that the inc_features.php file is loading up on the page no matter what? Irregardless of the plugin's call-phrase of $photopost_features being listed somewhere in the template?

And because of that, its important to NOT have plugins activated if you aren't using them because they are loading all these files and what not, just waiting to "print" them out on the page once the proper call-phrase appears to make them visible?

Forgive my crappy explanations and question. Not very good at getting my confusion to not sound confusing when I need help.

Again, all I'm asking here is HOW the system works, not how to get a certain plugin to work here or there. I totally understand all the hook locations, I just don't get how it nows what file to load since nowhere in the xml file does it say anything about THISXXX = THISWWW