APC, or Alternative PHP Cache, is a PHP module that caches the output code of database-driven script software apps. Dynamic PHP Internet sites store their content within a database which is accessed whenever a visitor opens a webpage. The content which has to be shown is retrieved and the code is parsed and compiled before it's delivered to the visitor. These actions need some processing time and involve reading and writing on the server for every single page which is accessed. While this can't be avoided for Internet sites with regularly changing content, there're numerous sites that feature the very same content on a lot of of their webpages constantly - blogs, informational portals, hotel and restaurant websites, etc. APC is exceptionally useful for this type of sites as it caches the previously compiled code and shows it when visitors browse the cached webpages, so the code doesn't have to be parsed and compiled repeatedly. This will not only greatly reduce the server load, but it will also increase the speed of any site a few times.