If you could save many people from great harm or save only one person from harm, many of us would think that we should try to save as many as possible. The thought is saving more lives and preventing more harm is morally better than saving fewer or preventing less harm. This is the thought behind consequentialist moral theories, of which utilitarianism is the most well known. According to utilitarianism, our actions should minimize pain and suffering, and promote happiness as much as possible. This is a natural thought and there are strong reasons in support of the idea that we should try to maximize good outcomes.
Still, there are some interesting complexities in applying the basic idea. For instance, how do we identify which consequences are the morally relevant ones? And how do we determine who is affected and thus for whom the consequences matter morally? Utilitarianism says we should be impartial, that is, recognize the equal moral worth of all persons affected. How then should we think about our moral duties and responsibilities to particular persons, such as family and friends?