A Cordova/PhoneGap developer is responsible for creating mobile applications using HTML, CSS, and JavaScript through the Cordova/PhoneGap platform. This platform allows for the development of cross-platform applications that can run on multiple mobile operating systems. The developer's tasks include designing and implementing user interfaces, debugging and improving application performance, integrating with APIs for added functionalities, and ensuring the apps are compatible with different devices and resolutions. They also conduct testing, troubleshoot bugs, and maintain the codebase for future updates. They often collaborate with other team members, such as UI/UX designers and backend developers, to ensure a smooth user experience.