Deep learning is an area of data science that is experiencing rapid advancement and generating a lot of excitement. Some deep learning models are better at certain types of image recognition than humans. When stories in the media mention artificial intelligence, they are usually referring to deep learning models.

Deep learning models are very complex although several of the concepts are similar to the ML concepts we have discussed so far in this chapter (such as the bias-variance tradeoff). Deep learning models can have millions of features and can take days or weeks to train.