There are many different types of food co-ops. I have attached a link to a good source of explanation.
Just the first paragraph, for more please click the link.
A food co-op is a collectively owned grocery store. Most frequently, a food co-op focuses on making natural foods more affordable for co-op members, although other products may be carried as well. There are a number of different styles of food co-op, but all of them share common values of group management and decision making, social responsibility, and equality. Towns of all sizes have food co-ops ranging from very small to quite large, and it is usually easy to find a food co-op near you.