Reciprocity is the idea that people feel obligated to repay others for the things they've done for them. For example, if a neighbour helps you move furniture, you might feel obligated to help them with something in return. Reciprocity is a social norm that refers to the idea that people should respond in kind to the actions of others. In other words, if someone does something nice for you, you should return the favor. Reciprocity is important in economics because it underlies a lot of human behavior. For example, reciprocity is the basis for many social interactions, such as gift-giving and favors. It's also one of the key factors in building trust and cooperation between people.