A Framebuffer (or sometimes Framestore) is a video output device that drives a video display from a memory buffer containing a complete frame of data.
The information in the memory buffer typically consists of color values for every pixel (point that can be displayed) on the screen. Color values are commonly stored in 1-bit binary (monochrome), 4-bit palettized, 8-bit palettized, 16-bit highcolor and 24-bit truecolor formats. An additional alpha channel is sometimes used to retain information about pixel transparency. The total amount of the memory required to drive the framebuffer depends on the resolution of the output signal, and on the color depth and palette size.
Framebuffers differ significantly from the vector displays that were common prior to the advent of the framebuffer. With a vector display, only the vertices of the graphics primitives are stored. The electron beam of the output display is then commanded to move from vertex to vertex, tracing an analog line across the area between these points. With a framebuffer, the electron beam (if the display technology uses one) is commanded to trace a left-to-right, top-to-bottom path across the entire screen, the way a television renders a broadcast signal. At the same time, the color information for each point on the screen is pulled from the framebuffer, creating a set of discrete picture elements (pixels).
Read more about Framebuffer: History, Display Modes, Color Palette, Memory Access, Virtual Framebuffers, Page Flipping, Graphics Accelerators