Image or video output is just the reverse of input. Thus an area of memory is set aside for the ``frame buffer''. Data written here will be read by the video controller, and used to control the signal to the display's electron gun for intensity of each of the colors for the corresponding pixel. By changing what is in the frame buffer once per scan time, you get motion/animation etc. So to play back digital video from disk, typically, you read it from disk to the frame buffer at the appropriate rate, and you have a digital VCR (presumably with digital video tapes)!
``Video RAM'' is not usually quite the same as other memory since it is targeted at good row then column scans rather than true RAM access.
VRAM stores n bits of each of RGB If n=8 , it is known ``True Color'' n < 8, can have colour maps then typically values are indexes to tables. These Color maps lead to flicker or false colour n=1 , is just plain monochrome.