Video memory is memory located on the video card, in some cases located on the motherboard, that is accessible by the video and computer processor. With more video memory, the video card and computer are capable of handling more complex graphics at a faster rate.
As can be seen in the above picture, video memory is usually an IC that is integrated into the video card and not a removable memory module like the memory in your computer. Video card memory may be as low as 8 MB on older video cards and up to several gigabytes on newer video cards.
Like RAM in a computer, video memory temporarily stores data relating to graphics. As new graphics data comes in to the video card, it replaces graphics data no longer needed in the video memory. When a computer is turned off, any graphics data in the video memory is removed.