A central processing unit, usually called a CPU, is the main chip in a computer that does the actual thinking and calculating. Every time you open an app, type a sentence, or play a game, the CPU processes millions of instructions per second to make it happen.

Think of the CPU as the brain of the computer. Just like your brain receives information from your eyes and ears, processes it, and tells your body how to respond, the CPU receives data from the keyboard, mouse, and other parts of the computer, processes that information, and sends instructions back. When you click to open a file, the CPU figures out where that file is stored, retrieves it, and helps display it on your screen, all in fractions of a second.

The CPU works with other computer components: memory (RAM) stores information the CPU needs right now, the hard drive stores files for later, and the graphics card handles images. But the CPU coordinates everything, like a conductor leading an orchestra.

Modern CPUs contain billions of tiny electronic switches called transistors packed onto a chip smaller than a postage stamp. The faster and more powerful the CPU, the quicker your computer can run programs, load websites, and handle complicated tasks. When people say a computer is “fast” or “powerful,” they're often talking about its CPU.