hi there.
Yes this is a server OS. The main use is to centralize resources (files, policy, computer) and to do so, usually you install Active Directory. It's quite mandatory that you have clients which can connect to the server, otherwise they must sit in front to the server in order to work.
You have 2 choices to connect users:
Add workstation to the domain so the power to calculate things(running programs) is taken from the PC itself, or you can use terminal server, and in this scenario yours clients can have only a keyboard, mouse, screen and a network card. Which are called THIN CLIENT. In this way clients are on the server and they use its resources!
Usually you connect clients and server via a switch.