While the term deep learning was first associated with neural networks in 2000 by Igor Aizenberg and colleagues, it has only become popular in the last 5 years. Prior to this, we called this type of algorithm an artificial neural network (ANN). However, deep learning refers to something broader than ANNs and includes many other areas of connected machines. Therefore, to clarify, we will be discussing the ANN form of DL for much of the remainder of this book. However, we will also discuss some other forms of DL that can be used in games, in Chapter 5, Introducing DRL.