Religion is the unified system of beliefs and practices that give people something sacred to believe in, someone or something to worship, and a code of conduct to live by. It can also be a community that supports and nurtures its members. People are surprisingly universal in their desire to belong and feel part of a community. This is one of the most basic human needs and it has led to the development of many religions throughout history. It is also why so many of them conflict and even fight. There are more than twenty major world religions today. But it is difficult to define what religion really is because a social genus can exist in more than one culture without being present in all of them, and there are people who have no views on an afterlife, supernatural beings, or explicit metaphysics, for example.

Nevertheless, there are still three broad ways that scholars have tried to define religion: a substantive definition, a functional definition, and a social formations theory. Substantive definitions of religion focus on what people think about or believe in, usually regarding spirituality or the afterlife. This is the approach of Emile Durkheim, who defines religion as whatever system of practices unites a group of people into a moral community (whether or not that system involves belief in any unusual reality).

A functionalism view of religion focuses on what it does for a society, regardless of its specific beliefs or practices. It was the focus of much of the work of Émile Durkheim, and it continues to influence sociological thinking about religion to this day. Social formations theory, on the other hand, tries to describe how social structures, beliefs, and values interact to create a religion. It also focuses on how religion influences human lives.

The most common way that scholars have discussed religion is as a social phenomenon. They have looked at its effects on societies and on individuals, including the role it plays in social relations and human psychology. In this context, religion can act as a source of pride and unity, but it can also be a cause of conflict, stress, and violence, especially when it is used for selfish purposes. It can also be an inspiration for a more meaningful and fulfilling life, as seen in the examples of saints and other religious figures who have done so much good in the world. For this reason, most psychologists regard religion as an important aspect of human life and consider it worth studying.