Religion provides comfort and guidance, a basis for moral beliefs and behaviors, a sense of community and connection to tradition, and even (according to some research) health benefits. People who regularly attend religious services seem to be healthier, though it’s not clear if this is because of their religion or something else like the fact that they get more social contact or are encouraged to behave in healthy ways.
Most religions are founded on some form of hope, which can take many forms: a desire for immortality or life after death, for a loving creator who watches over humanity, or for an ultimate meaning to human existence. The reason for this hope is unclear, but it may reflect a need to give order to the uncontrollable forces of nature or an attempt to appease those forces and gain their favor.
The concept of religion has been the subject of much debate in social science, including arguments over whether it is better to work with open polythetic definitions that allow different sets of properties or closed monothetic definitions that limit the set to one property. The latter approach tends to have a stronger claim to accuracy, but it also tends to be less useful for comparisons of the different religious traditions. It is, however, sometimes necessary to use this method in the interests of clarity and focus.