A frame buffer is a portion of memory in a computer or graphics device that stores the image or video data that will be displayed on a screen. The frame buffer holds the pixel values for each point on the screen and updates those values as the image or video changes.
The video controller, also known as a graphics controller or display controller, is a hardware component that controls the display of images or video on a screen. The video controller retrieves image or video data from the frame buffer and sends it to the display device. The video controller also performs other functions such as color management, gamma correction, and scaling.
In a typical computer system, the CPU (central processing unit) processes data and sends it to the frame buffer in the video memory. The video controller then reads the data from the frame buffer and sends it to the display device to be shown on the screen. The video controller can also include additional hardware such as a video scaler or a video processor to enhance the image or video quality before it is displayed.