CPUs (Central Processing Units) and GPUs (Graphics Processing Units) are both processors, which are the chips that do the actual computing work in a device. They differ fundamentally in their design and purpose. A CPU is the main brain of your computer. It runs your operating system, your browser, your apps — basically everything. It has a handful of powerful cores (usually 4 to 16) that can each handle complicated instructions and switch between tasks quickly. In contrast, GPUs were built with thousands of small, simple cores that all work in parallel. They were designed to be the chips that drew images on your screen (think rendering games or video), but this same functionality made them optimal for training and running neural networks. Because of their differing structures, a task that would take a CPU hours can take a GPU minutes.