In our scriptures, there are three words in descending order, for almighty God, Brahman, Ishwar and Bhagavān. Brahman is infinite, shapeless and without any qualities. It is the supreme power, supreme existence. It is neither masculine nor feminine. Hence in Sanskrit the word Brahman is said to be of neutral gender.
When that Brahman wishes to become many from one, it manifests its maya which is the supreme power or Energy of its own Being. This Maya has three fundamental qualities. When the Supreme Being manifests itself in union with its maya, that Supreme consciousness is known as Ishwar, which means one who controls.
Maya constitutes of three qualities: Sattva (purity), Rajas (activity) and Tamas (darkness and inertia). For the creation of universe, the quality of activity or Rajas is required. Hence Brahmaji, the God of creation, is the presiding deity of Rajoguna (quality of activity). Lord Vishnu, who sustains the universe, is the presiding deity of Sattvaguna (the quality of serenity). Lord Shiva, the God who oversees the dissolution of this world is the presiding deity of Tamas (the quality of darkness and inertia). Thus Brahma is the Generator of the universe, Vishnu is the Operator of the universe and Shiv is the Destroyer of the universe. The first alphabets of Generator, Operator and Destroyer give us the word GOD.
When that God incarnates in human form, it is called Bhagavan. The Sanskrit word ‘avatār‘ for incarnation implies ‘avataran‘ i.e. the descent or coming down of the Divine. Meaning, that which is formless and without qualities takes a form and imbibes certain qualities, that which is unmanifested manifests, that which is infinite takes up the finite human form, that which is subtle becomes gross, that which is great becomes ordinary like us, and stays with us becoming so very much like us, but it brings along with it wonderful qualities and capacities. The process or phenomenon is called avatār or incarnation.
So, Brahma, Vishnu and Shiv all three of them can take incarnations. Lord Vishnu who sustains the universe is supposed to have taken 10 or 24 principal incarnations. But there are supposed to be many other incarnations also. And all of them are called Bhagavan e.g. Bhagavan Kurma, Bhagavan Varāha, Bhagavan Narsimha, Bhagavan Vāman, etc.
Just as a rich person is called Dhanwān, so also one who is full of ‘Bhaga‘ is called Bhagavan. Bhaga means six qualities: Prosperity, Virility, Success and fame, Wealth, Knowledge and spirit of renunciation. Hence one who has any or many or all of these qualities is addressed as Bhagavan. For Vaishnavas there is no greater deity than Vishnu while for Shaivas, Shiv is the supreme Lord.
Everyone should have faith and commitment towards one deity, knows as Ishta Deva. Vishnu means that which is spread everywhere and Shiv means beneficent. One who is everywhere, who sees everything, who is large hearted, who sustains all and yet has no ego, and does not expect anything in return from living beings, that being is Vishnu. Vaishnavas should mould their lives in this same pattern.
