IAMGAMEDEVELOPER - I did research about frame buffer, and this is the big picture of me about it. Basically, there are 2 models that I want to reveal, first is before rasterization stage, another is after rasterization stage. What is rasterization? It is a process of converting primitive into two dimensional image. For more detail information about rasterization process, it can be accessed in OpenGL website.
Screen is array of pixel. Imagine what is the size of array for storing pixels in your computer's monitor?
The second model is after rasterization process, it is no longer pixel, but fragment. Fragment has pixel data which consists of color and depth value. Each fragment will be tester under some operations, and if it is survived from the test, which means success, it becomes pixel. Finally, pixel has data which is called buffer, and after restoring the buffer, pixel will be ready to be displayed.