Using a laptop as a monitor for another computer allows you to not only mirror your computer's screen on the laptop but also extend it, meaning you can show different content on both screens.

If you see the same thing on both displays, you should start by making sure the displays are Extended instead of Mirroring ...

Project to this PC let you use the new Connect app on Windows 10 to project your phone or another PC to your computer screen.

Nex Computer announces its NexPad, a 12-inch portable monitor that can be attached to the top of your laptop screen.