A GPGPU developer designs and implements software that leverages the parallel processing capabilities of a Graphics Processing Unit (GPU) for general computing tasks, beyond just computer graphics. They optimize algorithms, manage data transfers between CPU and GPU, and ensure efficient usage of GPU resources. Their work involves understanding hardware architecture, using programming languages like CUDA or OpenCL, and debugging and profiling GPU code. They also work on enhancing the performance of applications in various domains, such as machine learning, scientific computation, image processing, and real-time systems, by exploiting the high computational power of GPUs.