Keras is an open-source software library designed for building and training deep learning models. It provides a user-friendly interface that simplifies the process of creating neural networks, making it accessible for both beginners and experienced developers. Keras supports various backends, including TensorFlow, Theano, and Microsoft Cognitive Toolkit, allowing users to choose their preferred computational engine. Originally developed by François Chollet, Keras has become a popular choice in the machine learning community due to its modularity and flexibility. It offers a range of pre-built layers, optimizers, and tools for model evaluation, enabling users to quickly prototype and experiment with different architectures.