The central processing unit (CPU or central processor) is a circuit that implements all the necessary control and arithmetic logic necessary to execute general-purpose programs.
Prior to the advent and proliferation of multi-core architectures and system on chips, the word 'CPU' was synonymous with 'processor' and 'microprocessor'. Today, the CPU is more often referred to as a core as it's often one component on a chip with many other cores and other units.
The central processing unit or CPU is a circuit designed to execute general-purpose programs, though some CPUs may have additional capabilities, called ISA extensions, designed to accelerate specialized workloads. The term 'central' comes from the fact that the CPU is the main processing unit of the system and all other components typically follow commands initiated by the CPU.