This small book aims to build a theoretical framework around the different concepts in which Food and Nutrition Security (FNS) is framed. It defines hunger and food security and gives a brief history of the development of the concept of FNS, focusing on the dimension of economic access, the main cause of food and nutrition insecurity. Next, concepts associated with FNS such as vulnerability, food sovereignty, human right to food, poverty and social inequality are addressed, since it is understood that the discussion of these categories of analysis is fundamental when studying access to food and nutritional security.