A Generative Adversarial Network (GAN) developer designs and implements GAN models, a type of machine learning system. They create two neural networks, a generator and a discriminator, that work against each other. The generator creates new data instances while the discriminator evaluates them for authenticity. The developer trains the models using large datasets, iteratively improving the generator's ability to create realistic data. They also ensure the model's efficiency and accuracy. GAN developers work in various fields, creating realistic images, improving video game graphics, generating human-like text, and more. They also address issues like model stability and overfitting.