Decision theory is the study of the reasoning that goes in an individual's choices. This is divided into three types of decision-making; normative, descriptive, and prescriptive. Normative gives advice on how to make the best decisions. Descriptive is the type that analyzes how existing, possibly irrational agents, actually make decisions. Prescriptive tries to guide us or give the procedures on how or what we should do in order to make best decisions.