A managed server differs in that we carry out the initial configuration, and you receive a machine ready for work.
First the basics of security are covered: changing the credentials, configuring the firewall, restricting remote desktop access and installing the current updates.
Then whatever the task requires is deployed: a web server and certificates, Remote Desktop Services, a database or business software. The scope is agreed before the work begins.
Backups and basic monitoring are set up separately — free disk space, processor load and service availability. This is the part most often forgotten when people configure things themselves.
After that the server stays under observation: updates, responses to failures and questions about how the system works all go through support. What is left for you is the work with the application itself.