Directus is a database management system that allows developers to offload data storage and management to an external system, making it easier to work with their data. Directus can be used to store data and expose it in multiple ways beyond the application. The Vonage Voice API is used to allow users to call into the "Movie Phone System," which interacts with the Directus database instance to handle tasks such as calling in, managing tickets, and displaying information on the web. A reusable Directus client is created to access the database, and a tunneling system like ngrok is used to establish a secure connection between the application and the Vonage servers. The application works by using an NCCOBuilder to build JSON for the NCCO, which is sent back to the user's phone after they dial in, allowing them to interact with the application through voice commands. The application uses Directus to store and manage data related to movies, showtimes, and tickets, and provides a workflow for users to cancel or purchase tickets based on their interactions with the system.