Wikipedia
Ishta-Deva or Ishta Devata ( Sanskrit: ईष्ट देवता, , literally "cherished divinity" from iṣṭa "desired, liked, cherished, preferred" and devatā "godhead, divinity, tutelary deity" or deva "deity") is a term denoting a worshipper's favourite deity within Hinduism.
It is especially significant to both the Smarta and Bhakti schools wherein practitioners choose to worship the form of God that inspires them. Within Smartism, one of five chief deities are selected. Even in denominations that focus on a singular concept of God, such as Vaishnavism, the Ishta Deva concept exists. For example, in Vaishnavism, special focus is given to a particular form of Lord Vishnu or one of his Avatars (i.e. Krishna or Rama), and similarly within Shaktism, focus is given to a particular form of the Goddess such as Parvati or Lakshmi. The Swaminarayan sect of Vaishnavism has a similar concept, but notably holds that Vishnu and Shiva are different aspects of the same God.