A secret society is a club or organization whose activities and inner functioning are concealed from non-members. The society may or may not attempt to conceal its existence. The term usually excludes covert groups, such as intelligence agencies or guerrilla insurgencies, which hide their activities and memberships but maintain a public presence. The exact qualifications for labeling a group as a secret society are disputed, but definitions generally rely on the degree to which the organization insists on secrecy, and might involve the retention and transmission of secret knowledge, denial of membership in or knowledge of the group, the creation of personal bonds between members of the organization, and the use of secret rites or rituals which solidify members of the group.
Anthropologically and historically, secret societies are deeply interlinked with the concept of the Mannerbund, the all-male "warrior-band" or "warrior-society" of pre-modern cultures (see H. Schurtz, Alterklassen und Mannerbunde, Berlin, 1902; A. Van Gennep, The Rites of Passage, Chicago, 1960).
Conspiracy refers to a group of persons united in the goal of usurping or overthrowing an established political power. Typically, the final goal is to gain power through a revolutionary coup d'état or through assassination.
A conspiracy is to be contrasted with a cabal. The two are similar but have quite different connotations; in contrast to a cabal, a conspiracy usually looks to overthrow a fixed power instead of usurping it from within.