12.1 What is Deep Learning?

Deep learning is a branch of machine learning that uses neural networks with many stacked layers to learn directly from raw data. Instead of an engineer hand-crafting the features, each layer learns to transform the data into more useful representations, with later layers building on earlier ones.

Think of a phone app that recognises Ethiopian coffee beans by photo. Early layers detect edges and colours, middle layers detect shapes like bean curves, and final layers decide the variety — all learned from example photos, not written as rules.