Explain the concept of scope hierarchy? How many scope can an application have?

The application can have multiple scopes. Some directives create new child scopes.

Each angular application consist of one root scope but may have several child scopes. As child controllers and some directives create new child scopes, application can have multiple scopes. When new scopes are formed or created they are added as a children of their parent scope. Similar to DOM, they also creates a hierarchical structure.