The three major components of a CPU are the arithmetic logic unit, the control unit and the cache. These components are integrated together as a single microprocessor that is mounted on the computer's motherboard.
The central processing unit is responsible for handling instructions passed to it by programs and input devices. The arithmetic logic unit handles the arithmetic and logic functions. The control unit is responsible for processing instructions that come from the computer's memory and activating the other components of the computer. The cache is the memory in which instructions are temporarily stored.
Though CPUs are still commonly used, computers no longer require them to function as they are able to use multiple processors in tandem.