Definition
A central processing unit (CPU) is the chip that executes a program’s instructions, performing the arithmetic, logic, and control a system runs on. It is often called the computer’s “brain,” though strictly speaking it only follows instructions — the loaded program decides what to do.
How it works
A CPU runs a fetch-decode-execute loop, relying on registers and layered caches to keep the pipeline supplied with data. Modern designs add multiple cores, superscalar issue, out-of-order execution, and branch prediction to extract more parallelism from both single and multiple threads.
Usage
Nearly every computing device — phones, laptops, servers — uses a CPU as its main processor. Workloads with complex branching and strong serial dependencies, such as compiling code or running databases and business logic, lean heavily on CPU performance.
Related and confusable terms
A GPU favors massive parallel throughput, while a CPU favors low-latency execution of intricate logic; a TPU is a tensor-focused ASIC. At the instruction-set level, x86 is one of the most widespread CPU architecture families.