Onboard
The motherboard may provide a number of video output options already integrated. For example, VGA, DVI, and HDMI may already be included on the motherboard.
Add-on Card
You can add on a separate video card for gaming or intense video needs. A video card will go into the expansion slots available in your computer. These adapter cards usually take up 2 slots in your computer case because there are usually fans built in to the expansion card to keep the video card cool. An add-on card can add additional display ports.