TensorFlow is an open-source machine learning framework developed by Google. It provides tools for performing numerical computation and defining, training, and evaluating machine learning models. TensorFlow's flexible architecture allows models to be deployed on CPUs, GPUs, and TPUs. It has a large ecosystem of tools and an active community. The TensorFlow architecture consists of a backend for efficient computation and a frontend Python API for building models. Key program elements include operations, graphs, sessions, tensors, variables, and placeholders.