How are multiple servers administered?

Question

System administration

I'm studying to be a computer network administrator, I can't understand. There is a local network, it has 3 servers. On one Active
Directory server with DHCP and DNS. On the other, a web server. On the third MS SQL. It is not clear to me how all this is administered. When one server is clear. A server OS is installed on it, for example, Windows Server and the necessary roles and components.
And when there are three servers, it turns out that you need to buy three monitors and three server OS? If the question seems strange to someone, I will immediately say that I have no experience.

Answer 1

Windows has RDP for remote connection.

Answer 2

And when there are three servers, it turns out that you need to buy three monitors and three server OS?

If all servers are under Windows, then of course, three licenses for server Windows - and even more, many programs cost money in themselves :)
But you need exactly one monitor (well, or two - it’s more convenient for them) - for the workplace. RDP for Windows, VNC/SSH for Linux - and that's enough for the most rosy ears...