APC, or Alternative PHP Cache, is a PHP module which caches the output code of database-driven script apps. Dynamic PHP websites save their content in a database that is accessed whenever a visitor opens a page. The content that has to be displayed is retrieved and the code is parsed and compiled before it's delivered to the site visitor. All of these actions need some processing time and involve reading and writing on the hosting server for each and every page which is opened. While this cannot be avoided for sites with regularly changing content material, there're various sites which have the exact same content on a number of of their webpages all of the time - blogs, informational portals, hotel and restaurant websites, etc. APC is exceptionally useful for this type of websites 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 all over again. Not only will this reduce the server load, but it'll also boost the speed of any website a few times.