What does the “private” modifier do?

Question

Considering "private" is the default access modifier for class Members, why is the keyword even needed?

Answer 1

The private modifier explains intent.

A private member variable is not intended for direct manipulation outside the class. get/set accessors may or may not be created for the variable.

A private method is not intended for use outside the class. This may be for internal functionality only. Or you could make a default constructor private to prevent the construction of the class without passing in values.

The private modifier (and others like it) can be a useful way of writing self documenting code.