An Address Book is a tool that allows you to store multiple contacts in a single list. Once you've stored your contacts, you can send an ad-hoc SMS or create a campaign targeting all of the contacts in your saved address book.
An Address Book also supports dynamic fields, which can help you build more personalized SMS messages. You can create an unlimited number of address books for your various requirements.
Create a new Address Book
To create a new address book navigate to Address Book > Create New. Provide a descriptive name for your address book, and then upload a .csv file containing all the necessary information. Note that only the "Number" field is mandatory. To help with populating the information, you can download a template that includes the following fields:
Number; First Name; Last Name; Company; Custom 1; Custom 2; Custom 3; Custom 4
If you want an idea of how to use information for a contact within an address book, you can read this article: