What is a CPU and what does it do?

The CPU (processor) is the main chip that runs all programs on your computer. Clock speed (GHz) and core count matter, but the generation and design matter just as much. A newer processor at lower speed outperforms an older one at higher speed.

The CPU runs all instructions for every program running on your computer. The speed matters (measured in GHz), the core count matters (how many tasks it can run in parallel), and the generation matters most of all — newer processors beat older ones even at lower speeds. The main CPU families you'll see are Intel Core, AMD Ryzen, and Apple Silicon.