Deontology is a duty-based ethical theory that focuses on acts being right or wrong based on whether they conform to moral rules and duties, rather than the consequences of the acts. Under deontology, the consequences of acts do not affect their morality - acts are prohibited if they violate rules of duty, even if they produce good outcomes. Some key aspects of deontology discussed in the document include it focusing on intention over consequences, certain choices being forbidden no matter their results, and the priority of doing the right act over producing good.