Ishtadevata

[1][2] It is especially significant to both the Smarta and Bhakti schools, wherein practitioners choose to worship the form of God that inspires them.

The Swaminarayan sect of Vaishnavism has a similar concept, but notably holds that Vishnu and Shiva are different aspects of the same God.

[3] The "worship of the five forms" (pañcāyatana pūjā) system, which was popularized by Adi Shankara among orthodox Brahmins of the Smārta tradition, invokes the five deities Ganesha, Vishnu, Shiva, Shakti, and Sūrya.

[4][5] This system was instituted by Adi Shankara primarily to unite the principal deities of the five major sects (Gāṇapatya, Śaiva, Vaiṣṇava, Shakta and Saura) on an equal status.

Within the Advaita schools it is believed that the human mind needs a concrete form to understand the divine that ultimately can never be defined.