Define Pages vs. EZ-Pages?

Can someone please provide some insight as to the differences between a "define page" and an "EZ-Page?" It seems that they are NOT the same thing, but then what is the intended use for each?

And after install, I have files named "page_2.php", "page_3.php", "page_4.php", "page_5.php" in /includes/languages/english -- are these EZ-Pages or define pages? Do they have special meaning (i.e., do they HAVE to be the first four pages used) or can I ignore them, rename them to something meaningful, etc.?

Thanks

The main difference as I use them is that you can have PHP code in define pages, but not in EZ pages (without some extra work).

By default, links to the define pages are displayed in the Information sidebox. EZ pages links can be displayed in the header, footer and sidebox and can be created to point to a define page, making them more flexible.

I rarely use the extra define pages (page_2, etc), but you can rename them or ignore them and even add more if you want.