This chapter introduces the readers to a new concept of machine learning, other than supervised and unsupervised learning. This concept is popularly known as reinforcement learning. Reinforcement learning is a kind of machine learning algorithm, where the model learns itself based on surrounding behavior and new technique of rewarding. This chapter will gradually teach the readers about each concept for understanding reinforcement learning in-depth, alongside a basic application with Python. This chapter will look at the concepts to understand why it is getting so much attention these days. This serves as a beginner's guide to reinforcement learning. Reinforcement learning is undoubtedly one of the most visible study areas at the moment, with a promising future ahead of it, and its popularity is growing by the day.