Spring Boot is a framework that reduces the complexity of setting up Java projects by providing sufficient documentation and structure, allowing developers to create standalone applications without relying on external web servers. The Spring Initializr tool generates the basic structure of a Spring Boot project for developers to get started quickly. To deploy a Java Spring Boot application with ngrok, developers need to set up their development environment, including installing Java Development Kit (JDK) version 11 and Maven 3.3 or newer, and then create and import a Spring Boot project using the Spring Initializr tool. The project structure is examined, and a web controller is created to handle HTTP requests made from users to the web application website. An ngrok tunnel is opened by initializing the ngrok client and tunnel, which connects the development version of the Java application running on the system to a public URL that Twilio can connect to.