In JPA there is a an attribute called referencedColumnName that can be set on @JoinColumn, @PrimaryKeyJoinColumn what is the idea behind this setting, can some on give a good example of where this would be used?

"referencedColumnName" property is the name of the column in the table that you are making reference with the column you are anotating. Or in a short manner: it‘s the column referenced in the destination table. Imagine something like this: cars and persons. One person can have many cars but one car belongs only to one person (sorry, I don‘t like anyone else driving my car).

Table Person
name char(64) primary key
age int

Table Car
car_registration char(32) primary key
car_brand (char 64)
car_model (char64)
owner_name char(64) foreign key references Person(name)
When you implement classes you will have something like

class Person{
   ...
}

class Car{
    ...
    @ManyToOne
    @JoinColumn(columnName="owner_name", referencedColumnName="name")
    private Person owner;
}

referencedColumnName