Q-Learning and Temporal-Difference Learning — Learning Value from Experience
The elegant idea of value functions becomes a practical algorithm through one trick: learn by comparing your prediction to a slightly-better prediction, and nudge toward the difference. Temporal-difference learning and its famous instance, Q-learning, are how an agent learns the value of its actions purely from experience — no model of the world required. This is the algorithm that first made reinforcement learning work, and its core idea quietly underlies much of the field.
Learn a guess from a better guess: temporal-difference learning and Q-learning nudge value estimates toward reward + γ × value-of-next, model-free, bootstrapping from every step. Off-policy learning, ε-greedy exploration, and why the Q-table can't scale — motivating deep RL.