APC, which is short for Alternative PHP Cache, is a framework used for caching the compiled source code of a script application, that can speed up a database-driven site several times. Every time a PHP web page is opened, the script pulls the website content that needs to be shown from a database, parses and compiles the code, and the result is shown to the visitor. While this is necessary for websites with frequently changing content, it's a waste of processing time and system resources for a website which doesn't change, for instance an informational portal that displays the very same content at all times. As soon as the web pages for such an Internet site are compiled, APC caches them and delivers them any time a user accesses them. Since this saves the time to collect content from the database and to parse and compile the program code, the Internet site will load considerably faster. APC is really useful particularly for scripts with massive source code.