Learn in the textbookThe Role and Basic Functions of an OS
DefinitionUser management (ユーザー管理) is the OS function that registers an account (アカウント) for each user and checks at login whether the person is really that user (authentication, 認証).
ExplanationEven when several people share one computer, separate accounts let the OS tell who is operating it. Users can also be gathered into groups (グループ), such as by department, and handled together. A user identified in this way is the "who" in the access rights covered later.
AnalogyIt works like the front desk of a members-only gym. You register as a member when you join, and on each visit your membership card is checked to confirm it is you.
Memory hookThe login screen is the front door of user management.