This book is intended to be a first introduction to deep learning. Deep learning is a special kind of learning with deep artificial neural networks, although today deep learning and artificial neural networks are considered to be the same field. Artificial neural networks are a subfield of machine learning which is in turn a subfield of both statistics and artificial intelligence (AI). Artificial neural networks are vastly more popular in artificial intelligence than in statistics. Deep learning today is not happy with just addressing a subfield of a subfield, but tries to make a run for the whole AI. An increasing number of AI fields like reasoning and planning, which were once the bastions of logical AI (also called the Good Old-Fashioned AI, or GOFAI), are now being tackled successfully by deep learning. In this sense, one might say that deep learning is an approach in AI, and not just a subfield of a subfield of AI.