Policy Gradients and Actor-Critic — Learning the Policy Directly
Value-based methods like Q-learning learn how good each action is, then act greedily. There's a different and often better approach: skip the value estimates and learn the policy itself, directly adjusting the probability of actions to get more reward. Policy gradient methods are how RL handles continuous control and stochastic strategies — and the actor-critic architecture that combines them with value learning is the foundation of the algorithms used to fine-tune today's language models.
Instead of learning values then acting greedily, learn the policy directly: adjust action probabilities to earn more reward. Why this handles continuous and stochastic policies, the high-variance problem, and actor-critic (and PPO) — the algorithm family behind RLHF and LLM alignment.