Deontology and Teleology are two specialist terms used to separate ethical theories. They difference between deontology and teleology, is in essence, the same as the difference between absolutist and relativist theories.
Deontology: This means the same as absolute. The ethical systems are based on some form of a rule system. Following a deontological system such as Kant, Natural Law or some forms of Christian ethics means that the moral thing to do is one that does not change from situation to situation. For example, according to Kantian ethics it will always be wrong to lie even if it saves someone’s life. This is because consequences are not taken into account and the universal law does not change.
Teleology: Teleological theories are the same as relativist theories. They state that the moral thing to do is one which will change from situation to situation because the consequence of an action is sovereign. Ethical systems like Utilitarianism and Situation ethics voice this belief. They suggest that lying can only be moral if it results in the most pleasure for the most people (Act Utilitarianism) or the most love towards the most people (Situation Ethics).
Below is a video outlining this and some key strengths and weaknesses: