Ethic of reciprocity
The ethic of reciprocity means doing nice things for other people, expecting that they will do nice things for you in return. For example, if your friend brings you a cupcake, you might buy one for them too. This is a way of showing that you care about them, and expecting them to care about you too.
Related topics others have asked about:
Empathy,
Eye for an eye,
General welfare clause,
Kali's morality,
Norm of reciprocity,
Reciprocity (cultural anthropology),
Reciprocity (evolution),
Reciprocity (international relations),
Reciprocity (social and political philosophy),
Reciprocity (social psychology),
Serial reciprocity,
Ubuntu (philosophy)