The global address book or address list is a shared list of all people contained in a company or organization (such as a school or hospital).
This read-only address list is accessed over the company computer network in order to search for people and find their contact information.

Administrators can add information or update the entries.
For instance, if a client wants to email a specific recipient within a company, the global address book can help them look up their email address in the directory. This saves the company’s customer service phone lines and email addresses from answering multiple queries about the contact information of specific parties.

By accessing the address book remotely, you can email employees or locate someone within the organization from any device with access to the internet.