Reinforcement learning (RL) has become an important component of modern artificial intelligence research and practice. It underlies systems that achieved strong performance at Go, enabled robot locomotion, and has been applied in the training pipelines of large language models. Yet the primary literature remains fragmented: scattered across thousands of specialist papers, dense with notation, and rarely synthesised into a narrative accessible to practitioners or researchers from adjacent fields. This paper presents an expository survey that prioritises conceptual clarity over formal rigour. Rather than cataloguing algorithms through convergence proofs or sample-complexity bounds, we aim to build understanding from the ground up, using intuition, analogy, and high-level pseudocode as primary expository tools. We acknowledge that this approach involves deliberate trade-offs: informal treatments can obscure edge cases, and readers transitioning to the primary literature will need to supplement this survey with more rigorous references. Our coverage is deliberately broad: we trace the conceptual arc from classical tabular methods—dynamic programming, Monte Carlo estimation, temporal-difference learning—through the deep RL revolution, to frontier topics including offline RL, reinforcement learning from human feedback (RLHF), preference optimisation, and model-based planning. The paper is structured as a self-contained introduction. A reader who has never encountered a Bellman equation will find a plain-language introduction; a practitioner familiar with Q-learning will find a unified framework that situates that knowledge within the broader landscape and connects it to methods such as PPO, CQL, DPO, and MuZero. Each algorithm is introduced as an intuition first, then sketched in readable pseudocode with at least one grounding analogy. The intended contribution is an accessible introductory reference—a single, coherent document through which a motivated non-specialist can acquire the vocabulary, conceptual map, and practical orientation needed to engage with the primary literature. It is not a replacement for rigorous treatments such as [1] or [2], to which the reader is directed for formal foundations.