Deontology refers to a group of moral views that focus on rules or prohibitions for action. Deontologists hold that these rules have moral importance independently of their effect on the good (consequentialism) or our character (virtue ethics). Different deontological theories focus on different concepts, but a common focus is the intrinsic moral value of principles like justice, rights, and duties.
In contrast with deontologists, consequentialists hold that principles like justice, rights, and duties are only instrumentally valuable; that is, they are only morally important considerations if acting in accordance with them will lead to the best outcome. Thus the difference between deontology and consequentialism is most strongly felt in cases where we can violate a deontological rule, like “do not murder”, in order to bring about great benefits to other people. For example, would it be morally permissible for a doctor to painlessly, secretly kill a patient in order to use their organs to save five other patients who would otherwise die without the procedure? Most deontologists would argue that killing the one to save the five is impermissible, even if this would lead to a better outcome, because the doctor would be violating the moral prohibition against killing innocent people.