A chain of command is an organizational system where instructions are passed from one person to another. It's widely used in military and other disciplined organizations (ex:police departments, & military ) in addition to civil organizations. So think about your local supermarkets they have regional managers, below the regional managers there are district managers ,below the district manger there is General manager then below them is a few assistant managers, below the assistant manger they have the clerks/stockers.
-Hope this helps