CPU, which is oftentimes called just "processor", is an abbreviation for Central Processing Unit. That's the core of each and every PC or hosting server, because it runs each of the calculations and logical input/output functions. Even though the performance of an Internet site or an app depends on other things too, like the amount of physical memory or the connectivity of the server, the rate at which a given processor works determines how quickly an application shall be executed. Later-generation processors have numerous cores that can severely improve their overall power and efficiency, since each core can handle numerous processes separately or several cores can take care of one process which requires a sizeable computing power. Because every single core functions at a particular speed, this architecture can be looked at as numerous separate processors cooperating.