An ExtJS job typically involves developing web applications using the ExtJS framework, a JavaScript library for building rich, interactive UIs. Developers in this role work with JavaScript, HTML, CSS, and Sencha ExtJS components to create responsive and data-driven applications. Responsibilities often include designing UI components, integrating APIs, and optimizing performance for enterprise-level applications. Employers may seek candidates with experience in front-end development, MVC architecture, and ExtJS versions like 4.x, 6.x, or later.