Friendship is considered one of the central human experiences, and has been sanctified by all major religions. The Epic of Gilgamesh, a Babylonian poem that is among the earliest known literary works in history, chronicles in great depth the friendship between Gilgamesh and Enkidu. The Greco-Roman had, as a paramount example, the friendship of Orestes and Pylades. The Abrahamic faiths have the story of David and Jonathan. Friendship played an important role in German Romanticism. A good example for this is Schiller's The Hostage (ballad). The Christian Gospels state that Jesus Christ declared, "No one has greater love than this, to lay down one's life for one's friends."(John 15:13).

In philosophy, Aristotle is perhaps best known for his discussion (in the Nicomachean Ethics) of philia, which is usually (somewhat misleadingly) translated as "friendship", and certainly included friendship, though is a much broader concept.

Cultural variations: (stub-section) A group of friends consists of two or more people who are in a mutually pleasing relationship engendering a sentiment of camaraderie, exclusivity and mutual trust. There are varying degrees of "closeness" between friends. Hence, some people choose to differentiate and categorize friendships based on this sentiment.