Supervised learning
Supervised learning is training a model on examples that people have labeled with the right answer, such as photos tagged "cat" or "dog" or emails marked as spam. The model learns to predict the label for new examples it has not seen. Its limit is the cost of labeling: every example needs a human answer.
Why it comes up
Fei-Fei Li's ImageNet, with millions of hand-labeled images, made large-scale supervised learning possible in vision, and Andrew Ng built much of his applied work on it; LeCun argues that labels are too scarce for machines to learn most of what they need this way.
Fei-Fei Li
Andrew Ng
Yann LeCun