As you may have gathered by this time, you, as a user of Project Athena, are aided by a fairly large number of services. You are served by NFS and AFS which bring you your files, by Kerberos which allows you to convince Athena that you are who you say you are, by Hesiod which allows you to look up information about many things, by Zephyr which allows you to locate users and communicate with them electronically, by the post offices which allow you to send mail - the list goes on. It would be virtually impossible for a single person to keep all of these services under control and consistent with each other. This is why we have Moira, the Service Management System. Moira is an alternate spelling for moera, which means fate. The three aspects of fate were Clotho, who spun the thread of life; Lachesis, who wove the thread into the tapestry of life setting a person's destiny; and Atropos, who cut the threads at the appropriate time. Similarly, Moira, the system, creates user accounts, controls the user's home placement and quota, and deactivates user accounts.
Moira is a very large database containing most of the information that is necessary to keep Athena running smoothly. Although Moira is not needed for someone to log in and use the system (unlike Kerberos, which must be available all the time), without it, nobody would be able to change anything about any service. This means you couldn't add anyone to a mailing list, create a new filesystem, or any number of similar operations.
Even though Moira controls a vast array of things and can perform several tasks, there are only two things that you will probably ever need to use Moira for: changing or inspecting lists and updating finger information. Both of these are explained in this section.