Deep learning is a form of machine learning that employs neural networks with multiple layers to analyze and learn from complex data. Keras and TensorFlow are two of the most widely used open-source frameworks for building and training deep learning models. Keras is a high-level API for neural network development that is designed to be user-friendly, while TensorFlow provides a low-level API for building and training models, as well as a high-level API with Keras. Together, these tools offer a robust and flexible platform for building and training deep learning models for a wide range of applications.