What is a nested class what are its advantages how it is defined and declared in C++?

The nested class is inside its enclosing class so that it has access to its enclosing class’s members . Like other members, a nested class can be declared static (or not). A static nested class is called just that: a static nested class. A nonstatic nested class is called an inner class.

A nested class is a class that is declared in another class . The nested class is also a member variable of the enclosing class and has the same access rights as the other members. However, the member functions of the enclosing class have no special access to the members of a nested class.9 Eki 2018

As mentioned in the section Nested Classes, nested classes enable you to logically group classes that are only used in one place, increase the use of encapsulation, and create more readable and maintainable code. … Use it if you are encapsulating a single unit of behavior that you want to pass to other code.