Nirguna Brahman, signifies in Hindu philosophy the that pervades the Universe, considered without form (guna), as in the Advaita school or else as without material form, as in Advaita Vedanta, the nirguna brahman is non-different from the supreme personality, God, whatever qualities we attribute to the divine. Nirgun Brahman is same as Para Brahman, i.e. Neither Male nor female.
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According to Advaita as taught by Sankara, saguna brahman refers to the lord identical with his own infinite jnanam. Sankara refers to him by names such as Shiva, Vishnu as specified in the vedas and upanishads. This saguna brahman is Paramartha, eternal, undecaying and non-differentiated from nirguna brahman. He is not affected even when he appears in this world as he controls the effects of his own maya shakti. Hiranyagarbha, the collection of deities in the Hindu pantheon of gods, is not saguna brahman as popularly miscontrued. Sankara clearly says that hiranyagarbha is called brahman only because of nearness to brahman. After many millions of years, the devotees who reach the worlds of gods (hiranyagarbha), will reach the state of vishnu. This is called advaita siddhi and this state can be reached here and now by one who is free from all desires and blessed by the lord.