PyTorch is an open-source machine learning library based on the Torch library, used for applications such as computer vision and natural language processing. PyTorch is a dynamic computational graph framework, which means that the user can change the graph on the spot during runtime. This makes it favorable to work with, compared to static computational graph frameworks like TensorFlow.

PyTorch is known for being user-friendly and flexible. It provides APIs for building and training neural networks, as well as tools for data loading and preprocessing. PyTorch also supports a wide range of features for computer vision, natural language processing, and reinforcement learning. PyTorch has a growing ecosystem of tools and libraries.