Pete Warden has an informative write up about the computing differences between the CPU and the GPU for the layman. It’s a simplified yet illuminating description. Go learn something!
Graphics Processing Units were created to draw images, text, and geometry onto the screen. This means they’re designed very differently than the CPUs that run applications. CPUs need to be good at following very complex recipes of instructions so they can deal with all sorts of user inputs and switch between tasks rapidly. GPUs are much more specialized. They only need to do a limited range of things, but each job they’re given can involve touching millions of memory locations in one go.