A Convolutional Neural Network (CNN) developer designs, builds and maintains neural networks that mimic the human brain's processing of visual data. They utilize CNN models to analyze visual data and identify patterns or features, primarily for image or video recognition tasks. Their work involves training and fine-tuning models, testing their performance, and tweaking parameters for optimal results. They also use programming languages like Python, and libraries such as TensorFlow or PyTorch. Their goal is to create efficient, accurate CNNs that can automate tasks, such as object detection, face recognition, or even medical image analysis.