That Bhagavat exists in the faces, the heads, the necks of all, he dwells in the cave (of the heart) of all beings, he is all-pervading, therefore he is the omnipresent Siva.

In plain words: The Lord (Bhagavat) is present in every face, head and neck, and lives deep in the heart of every living being. Because he is everywhere, he is called Shiva, the one who is present in all places.