Vibhutva means the quality of all pervading in Hinduism. It also means a holder and a controller. This nature or power of a person is also called vibhutva. Space or sky exists everywhere. Space is all pervading and its nature or quality is called vibhutva. Vibhu also represents prabhu, as it means control over of all.
The sun is also called vibhu, as he commands all movable and immovable beings. It is also confirmed in the Bhagavad Gita that one sun controls by his rays all the living beings of this world. His powerful status is called vibhutva.
A king is also called vibhu, and vibhutva represents his power, because he commands and controls all subjects of his kingdom. They will be entirely at his mercy.
He will take care of all his subjects. Not only does he protect them but also he looks after their welfare. That is why a king or government is vibhu and their power is called vibhutva.
A leader of a family, an association or a group is also called vibhu, as he looks after the welfare of his group and makes all his subordinates follow him. So his quality is called vibhutva. We can see this vibhutva in dumb animals, too. So, vibhutva is the nature of one who is omnipresent, mighty, powerful, supreme, etc. This quality is found in God. Therefore, many in vibhutva form worship God in different incarnations of God. Rama, Krishna, Narasimha, Vamana and six other avatars are called Vibhava avatara of God.