A GeoDjango developer uses the GeoDjango module, an extension of Django, to build location-based web applications. They handle spatial databases, geospatial fields, and APIs to create geolocation features. Their responsibilities include designing, implementing, and managing geospatial data models, running complex geospatial queries, and integrating with mapping tools like Google Maps or OpenStreetMap. They also handle data manipulation and analysis, and troubleshoot geospatial issues. A GeoDjango developer plays a crucial role in developing web applications where geographic information system (GIS) capabilities, such as location-based services, are required.