A CPU, or Central Processing Unit, is often referred to as the brain of a computer. It performs calculations and processes instructions, allowing the computer to run programs and execute tasks. The CPU interprets data and commands from software, making it essential for everything from browsing the internet to playing video games. Modern CPUs are made up of multiple cores, which means they can handle several tasks at once, improving performance. They work closely with other components like RAM (Random Access Memory) and motherboards to ensure smooth operation. Overall, the CPU plays a crucial role in determining a computer's speed and efficiency.