title: What is the difference between x_train and x_test in Keras?
body: <p>I've looked at a few tutorials to crack into Keras for deep learning using Convolutional Neural Networks. In the tutorial (and in Keras' official documentation), the MNIST dataset is loaded like so:</p>
  
  <pre><code>from keras.datasets import mnist
  
  (x_train, y_train), (x_test, y_test) = mnist.load_data()
  </code></pre>
  
  <p>However, no explanation is offered as to why we have two tuples of data. My question is: <strong>what are <code>x_train</code> and <code>y_train</code> and how do they differ from their <code>x_test</code> and <code>y_test</code> counterparts</strong>?</p>