CPU, that's frequently called just "processor", is an abbreviation for Central Processing Unit. This is the core of every laptop or computer or hosting server, as it runs all of the calculations and logical input/output functions. Although the performance of a website or an app relies on other things as well, including the amount of physical memory or the connection of the web server, the speed at which a given processor performs determines how soon an app will be executed. Later-generation processors have several cores which can seriously improve their overall power and efficiency, due to the fact that every single core can take care of a number of processes individually or a number of cores can take on one process that requires a significant computing power. Due to the fact that every core works at a particular speed, this architecture can be seen as numerous independent processors working together.