Which input device is used to input photo into the computer?

Skype

Well, he most basic one is a webcam, like the ones used for Skype or any other internet messenger. With proper software you can use it to capture still images or videos.

You can also use some digital camcorders which with proper drivers and software can act as webcams.

Alternatively u could get a tv card and connect other camcorders using video input on your card to capture video.

Hope that helps.