CPU, which is often called just "processor", is an abbreviation for Central Processing Unit. That's the core of each PC or hosting server, since it executes all the calculations and logical input/output operations. Though the performance of a website or an app relies on other things as well, like the amount of physical memory or the connection of the hosting server, the pace at which a given processor runs determines how soon an app shall be executed. Later-generation processors have numerous cores that can seriously increase their overall power and efficiency, since each core can handle numerous processes separately or several cores can handle a single process that needs a substantial processing power. As each and every core functions at a specific speed, this architecture can be seen as a few individual processors working together.