To be accountable means taking responsibility for the outcomes or consequences of a decision.
Why we need accountability :- Since civil servants exercise power, they have both responsibility and power , so accountability becomes a necessity so that the civil servant does not become authoritarian and be held accountable for the decisions that he takes.
Civil servants are accountable to? : Constitution, Law, Nation or Country, Democracy Organisational/Bureaucratic Norms, Profession and Professionalism, Family and Friends, Self, Middle Range Collectives, Public Interest/General Welfare, Humanity or the World and Religion or God.
Ex. Judiciary is a part of Political structure and thus is accountable to the Constitution, Constitution though being the supreme law of the land is accountable to the people of India. ( Constitutional Autochthony).
A quote on accountability :-