CPU, that is oftentimes called just "processor", is an abbreviation for Central Processing Unit. That's the core of any personal computer or web server, as it carries out all of the calculations and logical input/output procedures. Though the performance of a site or an app relies upon other things too, like the amount of physical memory or the connectivity of the web server, the pace at which a particular processor runs determines how quick a program will be executed. Later-generation processors have several cores which can severely boost their overall power and efficiency, because each and every core can take care of several processes individually or a number of cores can deal with a single process that requires a sizeable processing power. Because each and every core works at a particular speed, this architecture can be looked at as several separate processors working together.