APC, which stands for Alternative PHP Cache, is a framework used for caching the compiled source code of a script app, which can boost a database-driven website several times. Every time a PHP page is opened, the script pulls the content which should be loaded from a database, parses and compiles the code, then the result is shown to the visitor. While this is necessary for Internet sites with frequently changing content, it's a complete waste of processing time and system resources for an Internet site that doesn't change, for example an informational portal that displays identical content on a regular basis. When the web pages for such an Internet site are compiled, APC caches them and delivers them any time a visitor accesses them. As this saves the time to obtain content from the database and to parse and compile the program code, your website will load a lot quicker. APC is very useful in particular for scripts with massive source code.