A Grails developer designs, develops, and manages web applications using the Grails framework, a powerful Groovy-based web application framework for the Java platform. They leverage the framework's capabilities to create robust, scalable applications, integrating databases, handling user requests, and managing server responses. They often work with other technologies such as HTML, CSS, and JavaScript for front-end development. They also perform testing, debugging, and maintenance tasks, ensuring optimal application performance. Additionally, Grails developers collaborate with other team members, contribute to system design, and often participate in the entire software development lifecycle.