It's an app that connects to Microsoft Flight Simulator (2020) and will display the location of your aircraft along with some data points like its altitude, speed, autopilot status, etc. Data (location, frequencies, runways) for almost 37,000 airports worldwide is also included (sourced from OpenAIP).
Download the latest version from the releases section. Then, just run the executable. If you want to "uninstall", just delete the folder.
You're welcome to build the app yourself. Just download the repository. You'll need Visual Studio 2019 (Community edition is fine) and .NET Core 3.1 installed.