This address book is accessed over the computer network using LDAP protocol, CardDAV or some other electronic means.
Users can search it, look up other people (employees, students, members, etc.)
and obtain information such as their email address, phone number, work position and office location.
The application, such as an email client (e.g. SOGo, Zimbra or Thunderbird) can look up the email address in the GAL while the user has written only a part of the recipient's name.
LDAP directory can be used also for distribution of user certificates (X.509, OpenPGP).