CPU, that's often called just "processor", is an abbreviation for Central Processing Unit. This is the core of each and every laptop or computer or web server, as it performs each of the calculations and logical input/output procedures. Although the performance of an Internet site or an application is determined by other things too, like the amount of physical memory or the online connectivity of the server, the speed at which a given processor works determines how fast an application will be executed. Later-generation processors have multiple cores which can drastically improve their overall power and efficiency, as every single core can control a variety of processes individually or a few cores can deal with one process which needs a sizeable processing power. Since every single core operates at a particular speed, this architecture can be viewed as a few independent processors working together.