CPU, that's sometimes called just "processor", is an abbreviation for Central Processing Unit. This is the core of each PC or web server, because it runs each of the calculations and logical input/output procedures. Even though the performance of a site or an application is determined by other things also, like the amount of physical memory or the connection of the server, the speed at which a particular processor performs determines how quick an application shall be executed. Later-generation processors have multiple cores which can considerably boost their overall power and efficiency, since every single core can handle several processes individually or a few cores can take on one process which needs a significant processing power. Due to the fact that every single core operates at a specific speed, this architecture can be seen as a few separate processors cooperating.