The article explains how to build a simple IVR (Interactive Voice Response) system using Nexmo Voice and Spark Java. The goal is to create an IVR that allows users to input digits on their keypad, which will be processed by the service. To achieve this, you need to set up a Maven project, install the required dependencies, and configure Spark to host your web application. You also need to use Ngrok to expose your local development machine to the outside world. Once everything is set up, you can test your IVR system by calling the Nexmo number and entering digits on the keypad. The system responds with a message indicating the digit entered. To make it more useful, you can add functionality such as handling input events and connecting to databases. The article provides code examples and guidance throughout the process, making it accessible to developers of all levels.