CPU, that is often called just "processor", is an abbreviation for Central Processing Unit. That is the core of each laptop or computer or server, as it carries out all of the calculations and logical input/output procedures. Even though the performance of a site or an application relies upon other things too, like the amount of physical memory or the connection of the hosting server, the pace at which a particular processor works determines how fast an application will be executed. Later-generation processors have multiple cores that can significantly increase their overall power and efficiency, as every core can manage several processes individually or a number of cores can deal with one process which requires a significant processing power. As each core works at a particular speed, this architecture can be seen as a few independent processors cooperating.