CPU, that is often called just "processor", is an abbreviation for Central Processing Unit. This is the core of each laptop or computer or web server, since it runs all the calculations and logical input/output functions. Even though the performance of a website or an app relies on other things also, including the amount of physical memory or the connectivity of the hosting server, the speed at which a certain processor works determines how soon a program will be executed. Later-generation processors have a number of cores which can severely improve their overall power and efficiency, because every core can handle a number of processes separately or a few cores can take on 1 process which requires a considerable computing power. Since each and every core functions at a particular speed, this architecture can be viewed as numerous separate processors cooperating.