The basic difference between deontological thinking or ethics and teleological thinking or ethics is whether the code of ethics that`s being discussed is based on rules and principles of some kind, which would make it deontological, or whether the ethics are based on the outcomes of the decision, which would make it teleological. It`s not that the two ways of thinking disagree on what`s good or what`s bad, but people who think deontologically and people who think teleologically decide whether things are good or bad in a different way.
To try and give an example of the difference, suppose there`s some person who needs to make some sort of ethical decision. There are of course many decisions that have to be made all the time where the right decision is not always clear, and there may not be a one right decision at all. Different people can disagree on ethical questions, even after debating it. But, if the person makes their decision based on some sort of rule or principle, they`re a deontological thinker.
What exactly their rules or principles are doesn`t matter. It could be religious rules, personal rules, military rules, legal rules, or anything else, as long as the person is making their ethical decisions based on some sort of fixed principles. This person believes that they are doing the right thing as long as they make their choice consistently with what the rules say.