Deep Learning
A branch of machine learning that uses neural networks with many stacked layers to learn extremely complex patterns. Each layer transforms the data a little — from raw pixels to edges to shapes to 'this is a cat'. Deep learning is what made modern generative AI possible: diffusion models, LLMs, and video generators are all deep networks with billions of parameters. In practice you never touch the layers yourself, but knowing the concept explains why models need massive GPUs and data to train — and why they keep improving as both scale up.