From the Wikipedia:
"Common Ownership is a principle according to which the assets of an enterprise or other organization are held indivisibly rather than in the names of the individual members or by a public institution such as government. It is therefore in contrast to public ownership. Thus, rather than being “owners” of the enterprise, its members are held to be trustees of it and its assets for future generations. Common ownership is a way of “neutralising” capital, and vesting control of an enterprise by virtue of participation in it, rather than by the injection of capital, also in an example of business.
Many socialist movements advocate common ownership of the means of production as an eventual goal; making the distinction between collective ownership (such as corporate/private ownership and state ownership) and common property.
In political philosophy, common ownership refers to joint or collective ownership by all individuals in society. Common ownership of the means of production is advocated, or asserted, by communism and some forms of socialism. Common ownership differs from collective ownership. The former means property open for access to anyone, and the latter means property owned jointly by agreement. Examples of collective ownership include modern forms of corporate ownership as well as producer cooperatives, which are in contrast to forms of common ownership, such as a public park available to everyone.
Common ownership of land is an example of customary land ownership in tribal societies which predates and runs simultaneously to the arrangement of colonised alienated land. Tribes and families living on the land have common ownership through tradition." (http://en.wikipedia.org/wiki/Common_ownership)