understand JPA declared attributes of ManagedType

Question

JPA ManagedType has

public Set<Attribute<? super X, ?>> getAttributes()

public Set<Attribute<X, ?>> getDeclaredAttributes()

What are declared attributes? what are not declared attributes? Please explain by example.

https://docs.oracle.com/javaee/7/api/javax/persistence/metamodel/ManagedType.html