Three kinds of learning
Supervised Learning: this models p(y|x)
Learn to predict a real valued output or a class label
from an input.
Reinforcement learning: this just tries to have a good time
Choose actions that maximize payoff
Unsupervised Learning: this models p(x)
Build a causal generative model that explains why
some data vectors occur and not others
                                         or
Learn an energy function that gives low energy to data
and high energy to non-data
                                         or
Discover interesting features; separate sources that
have been mixed together; find temporal invariants etc.
etc.