If you are new to the field of Artificial Intelligence (AI) or machine learning, you might be wondering what reinforcement learning is all about. In simple terms, it is learning through reinforcement. Reinforcement, as you know from general English or psychology, is the act of increasing or strengthening the choice to take a particular action in response to something, because of the perceived benefit of receiving higher rewards for taking that action. We humans are good at learning through reinforcement from a very young age. Those who have kids may be utilizing this fact more often to teach good habits to them. Nevertheless, we will all be able to relate to this, because not so long ago we all went through that phase of life! Say parents reward their kid with chocolate if the kid completes their homework on time after school every day. The kid learns the fact that he/she will receive chocolate (a reward) if he/she completes their homework every day. Therefore, this strengthens their decision to finish their homework every day to receive the chocolate. This process of learning to strengthen a particular choice of action, motivated by the reward they will receive for taking such an action, is called learning by reinforcement or reinforcement learning.

You might be thinking, "Oh yeah. That human psychology sounds very familiar to me. But what has that got to do with machine learning or AI?" Good thought. The concept of reinforcement learning was in fact inspired by behavioral psychology. It is at the nexus of several fields of research, the most important being computer science, mathematics, neuroscience, and psychology, as shown in the following diagram:

As we will soon realize, reinforcement learning is one of the most promising methods in machine learning leading towards AI. If all these terms are new to you, do not worry! Starting from the next paragraph, we will go over these terms and understand their relationship with each other to make you feel comfortable. If you already know these terms, it will be a refreshing read with a different perspective.