Answer:
If your motherboard already has a VGA port, you do not need an additional graphics card. However, depending upon what you plan to do with your computer you may want one. Some motherboards come with fairly low-end graphics chipsets so if you plan to do much gaming, 3-d graphics or the like, you may find the onboard video is insufficient. The good news is that you can always add one on later if you discover you need one.