Administrator

The Admin or Administrator of a server is the person who takes responsibility for the server. It may be that the server is running from their machine, or that they simply have jurisdiction over a remote server, or in some cases part of one.

Terminology
The term Admin is not interchangeable with Op (short for "operator"). An op is a person designated, by the original administrator or other ops, to police the server on their behalf. There may be multiple ops, but only one admin in a server. There may be multiple admins, but only in browser multiplayer game. They basically are a co owner at some purposes.

Powers
Administrators have all of the commands available to ops, and also the advantage of the tools available from the server software. Admins have control over the selection and implementation of the map, and can choose the settings for the room, such as maximum number of players, players allowed from the same IP address, and the name and MOTD of the room. The admin can also ghost the room; chatting via the console, without being logged into the server.