Video card
Video cards have their own processor (called a Graphics Processing Unit or GPU).  The GPU is distinct from the main computer processor (called the Central Processing Unit or CPU).  The CPU's job is to process the calculations needed to make the computer function.  The GPU's job is to handle graphics calculations.  3D graphics calculations take a lot of CPU power, so having a video card to handle the graphics calculations lets the CPU work on other things like running computer programs.