TensorFlow is an open source machine learning platform created by Google, providing tools and libraries for building, training and deploying neural networks across servers, mobile and the web.
scikit-learn is a free, open source Python library for machine learning, offering simple tools for classification, regression, clustering, dimensionality reduction and model evaluation.
PyTorch is an open source machine learning framework, originally from Meta AI and now under the Linux Foundation, widely used for deep learning research and production with GPUs.