A worker cooperative is a type of firm that is owned and controlled by its workers. Members of a worker cooperative are those who have a functional working role through their contribution of labor. Only those working at the cooperative may be members.
A worker cooperative is governed democratically by its members, with each member getting exactly one vote. While some worker cooperatives have a flat decision making structure, others elect a board or managers who serve the membership. It is a choice between direct democracy or various levels of representation.
A worker cooperative is owned by its members in the sense the all the profits or losses are distributed to the members. The distribution may be equal among members or vary, as the members see fit. Common profit distribution methods are based on total hours worked or compensation.
Outside investors in a worker cooperative are functionally lenders, who have no governing control and are limited to a fixed return on their investment.
For a more detailed treatment see “The Democratic Worker-Owned Firm” by David Ellerman.