A website like this one involves the posting of a lot of code snippets and examples in a variety of development languages. Because code often looks a lot like a plain old bunch of textual gibberish, the ability to syntax-highlight the entry immediately makes it recognizable and thus useful to a programmer reading the entry.
WordPress.com has a useful feature built into it where it can automatically syntax-highlight code when placed within special shortcode markers, based on work by Alex Gorbatchev. Plugin author Viper007Bond together with the official Automattic company have taken this a little further, wrapping it up in a WordPress plugin form and releasing it to the public at large as SyntaxHighlighter Evolved!
Featuring support for a wide variety of languages, highlighting your code syntax is as easy as writing
[ php ]code[ /php ]
The plugin takes care of html entities and all that sort of encoding stuff, meaning that you don’t have to manually change your snippet in order for WordPress to properly display it! In addition, there are plenty of options you can employ within the shortcode blocks in order to extend the display functionality, like adding highlighted rows, line numbers, etc.
Powerful (and really useful) stuff! :)
Related Link: http://wordpress.org/extend/plugins/syntaxhighlighter