What are typical application areas of LDAP?

Central authentication and authorisation, management of users, groups, devices and applications, and central address books for mail clients; plus network access control in combination with RADIUS.

1. Authentication and authorisation: the directory is the central user store. Systems check over LDAP whether a user exists, whether the password is correct, and which rights the user has.
2. Resource management: information about users (name, e-mail, phone number), groups ("Admins", "Developers"), devices and applications in one place, so that every connected system sees the same data.
3. Address books: mail clients such as Microsoft Outlook query the central company address book over LDAP when you start typing a colleague's name.
4. Network access (WLAN, VPN): a RADIUS server checks the users against the LDAP directory before it admits their devices to the network.

The common theme is one source of truth: an employee is created, changed and disabled once in the directory, and every application that relies on it follows automatically.

Go deeper:

• LDAP usage (Wikipedia) — typical deployments and the LDAP URL scheme applications use.