Deep Learning is a promising field of Artificial Intelligence algorithms that have proven to be capable of solving a wide range of tasks including classification, object detection, regression, face recognition, augmented and virtual reality, self-driving cars and many more. This chapter introduces the reader to Deep Learning, its basic principles, and applications. It covers the essential elements of any Deep Learning system, as well as explains how to connect these elements to form a neural network. The reader will understand the reasoning behind the Deep Learning and why it is so useful nowadays. The training algorithm of the neural network is also covered in this chapter.