Most basic of all questions

[Stavros_McGillicuddy]

Is Proxmox an operating system?
If I load it on my Windows 10 NUC, will it overwrite Windows or is it an app that runs in Widpws?

 

[leesteken]

Basically, yes, it will overwrite.
Maybe more information about virtualization and hypervisors will help you?

 

[Dominic]

For testing (performance will be bad) you can download https://www.virtualbox.org/ and run Proxmox VE itself in a virtual machine