Using [brackets] to pull .php code into pages?

I recently installed the Shopp plugin to add a shopping cart to my WP site, and noticed something.

In my customization of the plugin, I encountered pages created by the Shopp plugin that consist of nothing except, say, “[account]”.

Looking in the shopp folder, there is a file called “account.php,” which is being called and rendered by that page. In the course of my modifications, it became necessary to do something similar on my own. Unfortunately, I couldn’t duplicate the functionality – my page printed “[example]” instead of pulling in example.php.

I wasn’t sure how to search for this, but I’m quite stumped, and would love some help.

Thank you!