APC, or Alternative PHP Cache, is a PHP module which caches the output code of database-driven script applications. Dynamic PHP sites hold their content in a database which is accessed whenever a visitor opens a page. The content that needs to be viewed is gathered and the code is parsed and compiled before it is delivered to the visitor. These actions need some processing time and include reading and writing on the hosting server for each and every page which is accessed. While this can't be avoided for Internet sites with regularly changing content material, there're various websites that have the same content on many of their webpages all the time - blogs, informational portals, hotel and restaurant websites, etcetera. APC is quite useful for this kind of Internet sites since it caches the previously compiled code and displays it any time visitors browse the cached pages, so the code doesn't have to be parsed and compiled repeatedly. This will not only reduce the server load, but it'll also raise the speed of any site many times.