APC, or Alternative PHP Cache, is a PHP module that caches the output code of database-driven script apps. Dynamic PHP Internet sites store their content inside a database that is accessed whenever a visitor loads a webpage. The content which has to be shown is retrieved and the code is parsed and compiled before it is delivered to the website visitor. These actions take some processing time and require reading and writing on the web server for every single page which is loaded. While this can't be avoided for websites with regularly changing content, there are many sites that have the very same content on many of their pages at all times - blogs, info portals, hotel and restaurant Internet sites, etc. APC is really useful for this kind of sites since it caches the previously compiled code and shows it every time visitors browse the cached webpages, so the code does not have to be parsed and compiled all over again. This will not only lower the server load, but it'll also increase the speed of any website many times.