CPU, which is often called just "processor", is an abbreviation for Central Processing Unit. That's the core of each computer or hosting server, because it runs each of the calculations and logical input/output procedures. Even though the performance of a website or an application relies on other things also, like the amount of physical memory or the connectivity of the web server, the rate at which a particular processor operates determines how quick an application shall be executed. Later-generation processors have a number of cores that can considerably improve their overall power and efficiency, because each and every core can take on several processes individually or a number of cores can take care of one process which needs a significant computing power. As each and every core functions at a certain speed, this architecture can be seen as numerous separate processors working together.