In Wikipedia: Cooperative

A cooperative (also co-operative or co-op) is an autonomous association of persons who voluntarily cooperate for their mutual social, economic, and cultural benefit. Cooperatives include non-profit community organizations and businesses that are owned and managed by the people who use its services (a consumer cooperative) and/or by the people who work there (a worker cooperative).

Several forms of co-operatives are explained in the Wikipedia article.

In International Labour Organisation‘s 193/2002 Recommendation on the promotion of cooperatives, it is stated: "a balanced society necessitates the existence of strong public and private sectors, as well as a strong cooperative, mutual and the other social and non-governmental sector". Along these lines, 2001 Nobel Prize winner Joseph Stiglitz has recently pointed out: "my research showed that one needed to find a balance between markets, government, and other institutions, including not-for-profits and cooperatives, and that the successful countries were those that had found that balance" (Joseph Stiglitz, Moving beyond market fundamentalism to a more balanced economy, in 80 Annals of Public and Cooperative Economics 348 (2009)); and moreover: "success, broadly defined, requires a more balanced economy, a plural economic system with several pillars to it. There must be a traditional private sector of the economy, but the two other pillars have not received the attention which they deserve: the public sector, and the social cooperative economy, including mutual societies and not-for-profits" (ibidem, 356).
Source: footnote 6, page 35 of Study on the implementation of the Regulation 1435/2003 on the Statute for European Cooperative Society (SCE), October 2010

The Statute for a European Cooperative Society (SCE), which has been implemented in all EU Member States and EEA countries, illustrates how a cooperative can be established under the laws of a country, and what are its typical features.

The International Cooperative Alliance has defined seven Co-operative Principles.

2012 is International Year of Co-operatives.