A Blender developer works on Blender, an open-source creation software. They write and debug code to create or enhance the software's features, such as modeling, rigging, animation, simulation, rendering, compositing, and motion tracking. They also maintain and upgrade the software to improve performance and user experience, fix bugs, and ensure compatibility with different hardware and software. Additionally, they often liaise with the user community to understand their needs and incorporate their feedback. Their expertise includes computer graphics, design, and various programming languages, particularly Python, which Blender uses for its API.