CPU, that's sometimes called just "processor", is an abbreviation for Central Processing Unit. That is the core of any laptop or computer or hosting server, as it runs each of the calculations and logical input/output procedures. Although the performance of a site or an app depends on other things as well, like the amount of physical memory or the online connectivity of the server, the rate at which a particular processor performs determines how soon an application will be executed. Later-generation processors have several cores which can seriously boost their overall power and efficiency, due to the fact that every single core can take care of several processes independently or several cores can deal with a single process which requires a sizeable processing power. Because every core operates at a particular speed, this architecture can be looked at as several independent processors cooperating.