There are two forms of worship: Temple worship and home worship.

The temple deity is installed, consecrated and fixed in the temple. The idol or image is awakened with Prana Pratishṭhā ceremony (establishment of breath or life in the idol, recitation of hymns and Mantras and the opening of the eyes). It is the descent of the divine in the idol.

Prana is breath. pratishṭhā is establishment, resting, position or the consecration of the idol. Mūrti Stapaṉa (=Ceremonial bath, as of an idol, in water, etc., purified by mantras) is ceremonial placement of idol in the temple. Tradition dictates that the eyes of the deity are sculpted open to the rising sun at Prāṇapratishṭha in the Garbhagṛiha, the sanctum sanctorum in the temple. Nyasa (sequential touching of the deity's body parts in which there are resident deities: Indra as hand, Brahma as heart, Sun as eyes...) Opening of eyes is the highlight of the ceremony, marking the completion of consecration of the idol. The deity retires to bed and awakens in the morning accompanied by ceremonies.

The temple deity is Acaram (Mūlavar) meaning he is immobile and fixed to the sanctum. The replica of the Mūlavar is the Uṟcavar, who goes on procession.

Pañćāyatana Puja is worshipping of five deities at home: Sun, Devi, Vishnu, Siva, Ganesa or Skanda. Ishta Devata = personal god: Gaṇeśa, Skanda... Pañćāyatana, popularized by Adi Sankara was in vogue long before his time.  These five deities can be icons or anicons, usually earth elements.

These five entities are one manifest personal god with five forms: The Saguṇa Brahman (Personal god with form: Brahman or the Absolute with qualities).

Worshipping Saguṇa Brahman with form is the step towards realization of Parabrahman (Supreme Brahman) without form.

Individual worshipper places his god of preference (Ishta Devata) in the center and the other four in four corners. The central deity according to one's preference could be Siva, Vishnu, Ganesa, sun or Goddess.

The Panchayatana can be carried during journeys, so the devotee can offer worship away from home.

(In the Advaita Vedanta tradition, Nirguna Brahman (Brahman without qualities) is Para Brahman. In other Vedanta traditions, it is Saguna Brahman (Brahman with qualities). In Vaishnavism and Shaivism, Vishnu and Shiva, respectively, are Para Brahman.-Wiki)