A graphic card is an interface between the processor and the display unit. The graphic card acts as the processing area for the graphics and the output. The graphic card uses the main Memory or RAM to store the images and continuously refreshes the display.
As graphics evolved into 3D images and 3D motion, graphic cards evolved into Accelerated Graphics Port that handles 3D motion, textures and a range of other effects that otherwise are CPU intensive. AGP cards contain special memory called Video RAM that frees up the main memory’s RAM and also allows for faster display rates and higher colors and resolution.