A few days ago I had a problem installing a video conferencing system, as I was unable to take the output of the codec display on a TV for some reasons. I was wondering could I have used the VGA port of the laptop as the display input just like that of a TV? If Yes how?
No, VGA ports on a laptop are output only.
To expand on AJ Henderson's answer, it would be extremely rare to find combined output/input ports for A/V on a computer, and certainly not combined input/output VGA. This is because the underlying technology to receive and process video is very different to that required to send it and uses high-frequency electronics which tend to be very picky about how they are laid out and connected. As a result adding both send and receive hardware to the same physical port is impractical, bordering on impossible. There are also implications of cost, naturally adding anything to a laptop that's not really needed by the majority of users will drive the price up, and nobody wants that!