The flow scope allows developers to group pages/views and demarcate the group with entry/exit points.
Between the request scope and the session scope, we have the CDI flow scope. This scope exists for a while in Spring Web Flow or ADF flow, and now is available in JSF 2.2 as well. Basically, the flow scope allows us to demarcate a set of related pages/views (usually, logic related) with an entry point (known as start node) and an exit point (known as return node).
Note
The flow scope is a good choice for applications that contain wizards, such as multiscreen subscriptions/registrations, bookings, and shopping carts. Generally speaking, any chunk of an application that has a logical start point and an end point can be encapsulated into the flow scope.
In the same application, we can define multiple flows, which can be seen as modules that are reusable and capable to communicate. They can be called sequentially, can be encapsulated as Matrioska dolls or can create any custom design...