A club is an association of people united by a common interest or goal. A service club, for example, exists for voluntary or charitable activities. There are clubs devoted to hobbies and sports, social activities clubs, political and religious clubs, and so forth.
The bar at the Savile Club in London
Historical image of Pall Mall with the Carlton Club, describing itself as the "oldest, and most important of all Conservative clubs"
Coffeehouse in London, 17th century
Meeting of the Saimaan Kameraseura photoclub on January 28, 1946 in Lappeenranta, Finland
A voluntary group or union is a group of individuals who enter into an agreement, usually as volunteers, to form a body to accomplish a purpose. Common examples include trade associations, trade unions, learned societies, professional associations, and environmental groups.
An annual general meeting of a typical small volunteer non-profit organisation (the Monaro Folk Society). Office bearers sitting are president, secretary and public officer.
Civil lecture at Budapest Brainbar