CPU, that is frequently called just "processor", is an abbreviation for Central Processing Unit. That's the core of every computer or hosting server, because it runs each of the calculations and logical input/output functions. Although the performance of an Internet site or an application depends on other things as well, such as the amount of physical memory or the connectivity of the web server, the pace at which a particular processor runs determines how soon an application will be executed. Later-generation processors have multiple cores which can seriously increase their overall power and efficiency, due to the fact that each core can take care of a number of processes independently or several cores can take care of a single process that needs a significant computing power. Because every single core operates at a certain speed, this architecture can be seen as a number of independent processors working together.