The processor (CPU) is the central processing unit, literally the central component in a computer. It's responsible for processing instructions and controlling the other components. Many processors include basic on-board graphics processors too so you can power a display without needing a separate graphics card. Intel and AMD rule the desktop processor market, and each has a wide range of models suited to different tasks and budgets. Low-end, dual-core chips can be had for 40€ or even less, but are only well matched to basic tasks, while the high-end is home to multi-core, high frequency monsters that can tear through the world's most intensive software. Before buying, ensure you've got a compatible motherboard and a cooler that can take the heat.