This document summarizes the concepts and basic processes involved in consumer behavior, emphasizing how understanding consumers' needs benefits both consumers and marketers. Understanding consumer behavior can allow companies to develop a commercial strategy that is better matched to consumers, which will increase demand and optimize the means to generate that demand. Some of the main challenges are the variability of behavior, its changing nature, and the complexities of studying it. The note delves into how consumer behavior can be studied in a systematic and precise way by using a wide range of theoretical approaches and models and how it can be affected by factors such as environmental influences (economic, political, technological and cultural context) and marketing actions. The document outlines the various psychological factors involved in decision-making (personality, lifestyles, beliefs and attitudes, motivation, perception and learning) as well as the non-psychological ones (age, sex, location, etc.) which allow the marketer to better understand the consumers’ buying habits. It explains the basic decision-making model in depth and how consumers’ behaviors can play an active role in generating value for the company or the opposite thanks to undesired behaviors such as boycotts, complaints and negative word of mouth. It wraps up by describing how to move consumers from habit buying to decision making.