Accountability refers to those aspects of responsibility involving giving a statistical or judicial explanation for events. Judgement may follow.
Accountability classically appears (or should appear) in the ambit of accountancy.
In politics, and particularly in representative democracies, accountability (sometimes known as transparency) is an important factor is securing good governance. It constrains the extent to which elected representatives and other office-holders can willfully deviate from their theoretical responsibilities, thus reducing corruption.
See also: campaign finance reform.