We went over Input and Output, and a GPU help with output, so why not?
It wasn't all that long ago when 3D images and animation on a computer was just a dream of the future. Today the raw power backing some GPUs is greater then that of other CPUs, some are even researching how to use the GPU for calculations other then those for graphics. The GPU must create images from data about 60 times per second, and there are a number of stages in this process. For most 3D images, the models are broken into many, many triangles that all must be put together in a common coordinate system. Lighting is also simulated though calculations, and alters the colors of some models. The location of the "camera" is taken into account (determining just what is put on your screen, and from what angle) and the triangles are filled in with color in a way that simulates various textures.
Luebke, David and Humphreys, Greg. How GPUs Work Computer.org : http://www.computer.org/portal/site/computer/menuitem.5d61c1d591162e4b0ef1bd108bcd45f3/index.jsp?pName=computer_level1_article&TheCat=1055&path=computer/homepage/Feb07&file=howthings.xml&xsl=article.xsl
The GPU is the actual Graphics Processing Unit on the Graphics Card. The GPU makes 3D images by making use of many vertices. To make those vertices all that is needed is various coordinates for them, though other information is also added. When a pattern of these shapes is noticed, one of those shapes is made to repeat as many times as needed instead of storing similar information more times then it has to be. There are two "pipelines" within the GPU, one for the vertices and another for more specific pixel information. After the two pipelines have done their thing, tests are done to find out what pixels are overlapping others, so that pixels that are blocked are more or less ignored during the desplay of the image.
Thibault, Michel. How does a GPU work. Supinfo-Projects : http://www.supinfo-projects.com/en/2006/graphics_board_gpu_work/
Though Tracy and Jeff do not go too deep into any specifics, they do offer a good overview of how the whole graphics card works. Graphics cards Are connected to your motherboard and your monitor (more then one monitor can be connected to some graphics cards). They have a processor that is much like a CPU, only built more for complex rendering then general computing. The card also has ram on it that is used to hold information on where pixels go as well finished images. The ram connects directly do a Digital-to-Analog Converter (a DAC) that converts the data into something your monitor can understand. A high end graphics card is not needed by most computer users.
Wilson, Tracy V and Tyson, Jeff.How Graphics Cards Work. HowStuffWorks : http://computer.howstuffworks.com/graphics-card.htm
This article offers a variety of information on the GPU by supplying the history of it. Mainly included because it was the first source I found that actually described a difference between a separate graphics card and an integrated one other then "separate cards are better". A graphics unit is "dedicated" if it has access to its own piece of memory (most all separate cards are dedicated). An integrated graphics unit must share the computers main memory with the CPU. Also, an integrated graphics unit may not be able to perform all the calculations needed to create a 3D image, and thus it shoves that work onto the CPU. This can slow your computer down greatly, as the CPU is already doing so much.
Graphics Processing Unit. Wikipedia : http://en.wikipedia.org/wiki/Graphics_processing_unit