Desktop screen into Laptop screen

Would you please let me know the following setup?

I want to run a PC desktop computer without the screen.
But using some male/male or male/female coaxial video cable, I wan to be able to see the what is being displayed in the PC computer - in my laptop.

Thus, the laptop serves as a single monitor for two different units - itself, and an external PC.

I hope, this is possible, but how?

Without some kind of video capture card in the laptop, I don’t think you can do that.

What you can do is use Windows Remote Desktop or VNC to see what’s on the PC, on your laptop, over the network.

Install realVNC client on your laptop and install realVNC server on your Desktop. You would have full control on both, is this enough?