Taking the guest's coat consists of helping the guest remove their coat, then hanging the coat up. As you can see, the diagram is much easier to understand than the description. Check out this reading list if you are interested. Flowcharts have been around since the early days of programming. They provide a simple graphical description of processes.
Flowcharts work great for building small programs.
However, you soon discover that as your program grows in size and complexity flowcharts do little to help manage that complexity. Advances in programming languages have helped manage complexity using hierarchically structured blocks. Because of the ubiquitous nature of hierarchies, B-liner diagrams are very much a general purpose tool. Anytime complex processes or objects need to be described, designed, or communicated, B-liner diagrams are an ideal tool. Using diagrams to help you think B-liner's hierarchical diagrams can be helpful in the early stages of formulating and solving problems.