Three-tier system of alcohol distribution
The three-tier system of alcohol distribution is a state-based regulatory alcohol control system comprised of suppliers (breweries, distilleries, wineries), distributors and retailers whose mission is to protect consumers from unsafe alcohol products and practices. The system was a response to post-Prohibition concern over consumption and consumer safety. It created a distinct separation between suppliers and retailers (wholesalers/distributors) that took away some of the power suppliers had over retailers.
Refer to TTB Beverage Alcohol to learn more.