A deep neural network is simply a neural network with many layers. That’s all there is to it, really.
On the figure below, on the left you see a simple neural network. The difference to a deep neural network (on the right) is clearly visible. The extra layers provide a huge increase in computational power, which have allowed deep neural networks to reach amazing performance in multiple tasks. Trending Announcing the new data maturity short course with Sameer Rahman and the Tesseract Academy