This is a really nice video (and analogy) to show you the difference between CPU and GPU.
Youtube: Adam and Jamie Paint the Mona Lisa in 80 Milliseconds! (HD) - YouTube
To demonstrate the power of CPU vs GPU, NVIDIA enlisted the help of the geeky duo that co-starred in the popular series “MythBusters.” Adam Savage and Jamie Hyneman took a highly-recognizable piece of art and reproduced it using a combination of robotics and paintballs. The video “MythBusters Demo GPU versus CPU” shows a colorful recreation using both CPU and GPU methodologies.