APC, or Alternative PHP Cache, is a PHP module which caches the output code of database-driven script software applications. Dynamic PHP Internet sites save their content within a database which is accessed whenever a visitor opens a page. The content which needs to be displayed is gathered and the code is parsed and compiled prior to it being delivered to the website visitor. All these actions take some processing time and include reading and writing on the web server for each page which is opened. While this can't be avoided for websites with regularly changing content, there are a lot of sites that present the very same content on a number of of their pages all of the time - blogs, informational portals, hotel and restaurant Internet sites, etc. APC is very useful for this kind of websites because it caches the previously compiled code and displays it whenever visitors browse the cached pages, so the code doesn't need to be parsed and compiled repeatedly. This will not only greatly reduce the server load, but it'll also raise the speed of any Internet site many times.