Deep learning is a form of machine learning that enables computers to learn from experience and understand the world in terms of a hierarchy of concepts by using multiple layers to progressively extract higher level features from the raw input. Because the computer gathers knowledge from experience, there is no need for a human computer operator formally to specify knowledge needed by the computer. Source: Deng, L.; Yu, D. (2014). "Deep Learning: Methods and Applications" . Foundations and Trends in Signal Processing. 7 (3–4): 1–199