Graphics Processor
So what is a graphics processor? Well, in order to answer this question I'm going to go ahead and dissect the phrase for you, because if you are asking that question... then I doubt you have dissected it for yourself. 'Processor' is the second word in the name of the thing, and assuming that you have read and seen what's on the previous page, so you should at least understand the basic concept of processing. So with the previous word being graphics, I assume that a graphics processor is a thing that processes the graphics, working like the CPU... kind of, but specifically for the graphics. The CPU is the Central Processing Unit, and the GPU is the Graphics Processing Unit, if that makes it more clearly understandable. GPU's like CPU's have transistors and make many calculations in a short ammount of time and they deliver triangles(+process polygons). - 'The first company to develop the GPU is NVIDIA Inc. Its GeForce 256 GPU is capable of billions of calculations per second, can process a minimum of 10 million polygons per second, and has over 22 million transistors, compared to the 9 million found on the Pentium III. Its workstation version called the Quadro, designed for CAD applications, can process over 200 billion operations a second and deliver up to 17 million triangles per second.' - http://www.webopedia.com/TERM/G/GPU.html
What does it for?
Why am the sky? There are many questions like this that are difficult to answer, but the one about the graphics processor is actually pseudo answerable for me, so here we go. A graphics processor (used for a 3D scene in this example) re creates the scene every time it needs to, replaces objects according to how you would see them, keeping the illusion believable, and it figures out what the lighting is doing and all these kinds of processes. With the graphics processor (a single chip processor) processing these things, it takes some of the strain off of the CPU, so that it can perform other processes and keep the computer running at the highest speed it can. It makes the CPU's job easier by doing some of its work so to speak.
Good GPU vs Bad GPU
This video shows some different ways that games can look bad due to a bad (or possibly non existent) graphics processor. The video shows that you can control the games, but the thing that doesn't work right due to the graphics processor is the display, and as previously mentioned this video shows different ways that a graphics processor or (graphics card) can be defective (showing the ways that a bad or non existent graphics processing unit can show the game wrong).
This is an example of a game in which the graphics are working perfectly fine (along with everything else), and the graphics working well is due to a functioning graphics card/ gpu.