Religion is the name of a large, diverse set of cultural forms. It is difficult to pin down and a variety of definitions have been offered. Some of these are “monothetic” in that they operate with the classical view that a concept can only accurately be defined by describing a set of necessary and sufficient properties. Others are more “open polythetic” and are designed to allow many different practices to be included in a category by evaluating them in terms of a family-resemblance structure. These have tended to focus on a function or role that the practice can play rather than on its content (see de Muckadell for a discussion of these).
Most religions deal in one way or another with salvation, either in a proximate sense, such as reaching a better or more fruitful life, or in an ultimate sense that deals with death and beyond. They also generally have a form of organization and worship, sacred books, rites or rituals, and special days, places and symbols.
Sociobiology suggests that the reason religions exist is to protect and transmit the means to attain the most important of human goals. Once those are successfully achieved, people can explore their own potentialities with a degree of confidence and security that would otherwise be dangerous or impossible. This exploration is known as somatic exploration (from the Greek word for body).