In Wicca and similar religions, the term coven implies a gathering similar to that implied by congregation in Christian parlance. It is composed of a group of believers gathered together for a ceremony of worship such as Drawing down the Moon.
During various witch hunts, however, those engaged in the prosecution (and/or persecution) of witches used the term in a sense close to that of the modern "criminal conspiracy". As these inquisitors regarded witchcraft as both a sin and a crime, an association of witches was therefore considered to be a pernicious threat to their religion and social order. (Witches were, by various Christian doctrines, considered to be involved in Satanism. However, modern Wicca is wholly separate from modern Satanism, and considerable doubt exists as to whether there was ever a strong connection between practitioners of witchcraft and Satanists.)
An intermediate view is often portrayed in fantasy stories and popular culture. In this usage, a coven is a gathering of witches to work spells in tandem. Movie portrayals have included, e.g. The Craft and COVEN (pronounced ko ven) (documented in the movie American Movie)