What is Apple's GPU?

Could you please elaborate on the specifics of Apple's GPU? I've heard it mentioned in the context of the company's devices but I'm not entirely sure what sets it apart from other graphics processing units. Is it a proprietary design? What are some of the key features or advancements it offers? How does it compare to other industry-leading GPUs? I'm curious to understand the technological underpinnings and how it contributes to the overall performance of Apple's products.