Answer - There are three ways to create Keras models: Firstly, by the Sequential model. This is very straightforward (a simple list of layers), but is limited to single-input, single-output stacks of layers. Secondly using the Functional API. This is an easy-to-use, fully-featured API that supports arbitrary model architectures. This is the Keras “industry strength” model. Lastly, by Model subclassing. Here you implement everything from scratch on your own. Use this if you have complex, out-of-the-box research use cases.