PyTorch is an open-source deep learning framework developed by Facebook's AI Research lab, now widely adopted across industry and academia. It provides a dynamic computational graph (define-by-run) that builds graphs on the fly during execution, contrasting with static graph frameworks. This design makes PyTorch exceptionally intuitive for researchers and practitioners who need to debug, experiment, and prototype quickly. The framework's core strength lies in its seamless integration with Python, native support for GPU acceleration via CUDA, and a rich ecosystem of tools for training, deploying, and optimizing neural networks. Understanding how tensors flow through models, how autograd tracks gradients, and how to structure training loops is fundamental to leveraging PyTorch effectively.