what are video capture card and video display card??

i give you a sample mind:
video capture card
many of them have tv-in ,in the computer skills, it belongs to a input device ,but if computer don't have it , also is no problem ,because the most important input device is keyboard and mouse. this card usually use to play the tv in the computer
video display card
a very inportant computer output device , if you don't have it , i think you can't use the computer and see the information from the computer