APC, or Alternative PHP Cache, is a PHP module which caches the output code of database-driven script software applications. Dynamic PHP websites store their content within a database which is accessed whenever a visitor opens a page. The content that has to be viewed is retrieved and the code is parsed and compiled before it's delivered to the website visitor. These actions take some processing time and include reading and writing on the hosting server for every single page that is loaded. While this can't be avoided for sites with constantly changing content material, there are a lot of sites that feature the very same content on a lot of of their pages constantly - blogs, info portals, hotel and restaurant websites, etcetera. APC is very useful for this kind of sites because it caches the already compiled code and shows it whenever visitors browse the cached webpages, so the code doesn't have to be parsed and compiled all over again. Not only will this decrease the server load, but it will also increase the speed of any website several times.