TensorFlow, theano and Keras are deep learning frameworks. TensorFlow and theano are more flexible and difficult to learn. They are actually a differentiator
.Keras is actually the interface between TensorFlow and Keras (Keras as the front end, TensorFlow or theano as the back end). It is also flexible and easy to learn. You can think of keras as an API encapsulated by tensorflow.
what do you mean by using Kears as the front end and tensorflow and theano as the back end?