APC, which is short for Alternative PHP Cache, is a framework used for caching the compiled source code of a script app, which could boost a database-driven site several times. Any time a PHP web page is accessed, the script pulls the content which has to be loaded from a database, parses and compiles the program code, then the result is displayed to the visitor. While this is necessary for sites with frequently changing content, it's a complete waste of processing time and system resources for a website that doesn't change, for instance an informational portal which displays the exact same content at all times. As soon as the webpages for such a site are compiled, APC caches them and delivers them every time a visitor opens them. As this saves the time to request content from the database and to parse and compile the program code, your website will load a lot faster. APC is very effective in particular for scripts with larger source code.