dicko is right. I am using the Asterisk Phonebook module in the Admin section of FreePBX 13 GUI. When writing custom context checks in the dial plan, I am using DB_Exists/Result to successfully query data, meaning that phonebook looks like it is being stored in AstDB.
Here is a more up to date link:
https://wiki.asterisk.org/wiki/display/AST/Asterisk+Internal+Database