title: What does "model.trainable = False" mean in Keras?
body: <p>I want to freeze a pre-trained network in Keras. I found <code>base.trainable = False</code> in the documentation. But I didn't understand how it works.
  With <code>len(model.trainable_weights)</code> I found out that I have 30 trainable weights. How can that be? The network shows total trainable params: 16,812,353.
  After freezing I have 4 trainable weights.
  Maybe I don't understand the difference between params and weights. Unfortunately I am a beginner in Deep Learning. Maybe someone can help me.</p>