Hi,
the self means compared to its parent.
so checking "SELF" will return the rotation of this gameObject within its parent transform. The confusing part is that if it's not parented, then it's the same value as if you selected "WORLD"
do this test. have a moon parented to the earth.
if you rotate the earth, the "Self" rotation of the moon doesn't change, but the "World" rotation of the moon does.
Does that clarify things?
bye,
Jean