Remembering the deity and internally building a relationship with (or through) them is considered essential to the practise. 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. Just as one can understand the abstract concept of a color only after one has seen a concrete form, one can only realize the deity through a form of murti. In contrast, the Dvaita schools believe the Supreme Being to possess a divine form, and offer worship to their Ishta-Deva as either a representation or direct expansion of the Supreme Person. For example, Vaishnava schools offer worship exclusively to murtis of Vishnu, or his associated avatars such as Krishna or Rama.
