The tutorial provides a comprehensive guide for building a REST API using Strapi and integrating it with a Next.js application to manage and generate invoices. It starts with setting up a Strapi project, creating an invoice collection with various field types, and configuring roles and permissions to allow data access from the Next.js app. The frontend is developed using Next.js and styled with Tailwind CSS, featuring a form interface for entering invoice details which are dynamically managed using React's useState and useReducer hooks. The tutorial covers functionalities such as adding, removing, and calculating total invoice items, and demonstrates how to send invoice data to the backend using Axios, as well as generating printable invoices. The complete code is available on GitHub, and the tutorial emphasizes the ease and power of using Strapi for backend development.