The Absolute, the source of all being, the unnameable, the one without a second, the numinous, that which is inherent in everything.
Vedanta philosophy paraphrases Brahman with ’neti neti‘, not this, not that.
Devotees of Vishnu, the Vaishnavas, personify Brahman with Vishnu.
Devotees of Shiva, the Shaivas, personify Brahman with Shiva.
Devotees of the Goddess, the Shaktas, personify Brahman with the Goddess.
Smartas personify Brahman with Vishnu, Shiva, Ganesha, the Goddess, the sun.
Personal Brahman is Brahman saguna, God with form/shape.
Impersonal Brahman is Brahman nirguna, God without form/shape.