This is in good old DOS batch language. It is still working as of Pro 2.5. (Thank you, Esri install team!)
The point of putting an install script together is to make installs easier and secondly to ensure your users have a consistent deployment with options you want. For example, this script allows you to block software updates so the administrator controls when ArcGIS Pro gets updated, keeping your users all on the same version of the software to avoid compatibility problems and user confusion. This script also saves log files so if something goes wrong in the install you can look at the log file for clues as to what went wrong (mostly commonly in my experience: .NET needs updating).
