A standalone system has an active directory built onto itself meaning that users can be created on the server itself and is independent from a company directory.
eg. If your system has an account called 'admin' and password is Promax123 by default, it is likely that your system is a Standalone system.
A Domain Joined System is a server that was joined to an already existing domain meaning that all the users on your network were created and controlled by an IT team.
eg. If you have a company email/username that you use to log into your computer but also in the Platform UI.
eg. If there is an admin account has another name it goes by that the IT team had created to access the server. General accounts can be something like PromaxSVC or PromaxService as examples.
Domain joined systems have specific created users and admin accounts that Promax does not have access to.
If Promax support is requested, the admin password will need to be known or someone on staff be present when accessing the server.
Locked accounts are not controlled by the server. Please see article here.