Forms of common ownership exist in every economic system. Common ownership of the means of production is a central goal of communist political movements as it is seen as a necessary democratic mechanism for the creation and continued function of a communist society. Advocates make a distinction between "collective ownership" and "common property" as the former refers to property owned jointly by agreement of a set of colleagues, such as producer cooperatives, whereas the latter refers to assets that are completely open for access, such as a public park freely available to everyone.