APC, or Alternative PHP Cache, is a PHP module that caches the output code of database-driven script apps. Dynamic PHP websites hold their content inside a database which is accessed whenever a visitor loads a page. The content which needs to be viewed is gathered and the code is parsed and compiled prior to it being delivered to the visitor. These actions need some processing time and require reading and writing on the server for each and every page that is opened. While this can't be avoided for Internet sites with constantly changing content, there're various sites that offer the same content on many of their pages constantly - blogs, informational portals, hotel and restaurant sites, and many others. APC is really useful for this kind of Internet sites since it caches the already compiled code and displays it whenever visitors browse the cached pages, so the code does not have to be parsed and compiled all over again. Not only will this decrease the server load, but it will also raise the speed of any site several times.