What is a "capture card"?

Question

Can anyone tell me and describe to me, what a "capture card" is?

Answer 1

It is an add-in computer board or a USB plug-in device that is designed to "capture" either video or a still frame from a video, and then convert it into a digital format that can be stored on a hard drive.  

Typically, a capture card has video inputs so that video can be played back on a device like a VCR and then the video signal runs into the capture card, which converts it from an analog signal to a digital signal.  It can then make a movie file and/or a still image (jpeg).