جَاءَ زَيْدٌ نَفْسُهُ.
“Zayd himself came.” «نَفْسُهُ» is semantic emphasis.
جَاءَ أَبُو حَفْصٍ عُمَرُ.
“Abū Ḥafṣ, that is ʿUmar, came.” «عُمَرُ» is explanatory apposition.
Emphasis answers “Was it he himself?” Explanatory apposition answers “Which person do you mean?”