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 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 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 worshiping 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).
Worshipping Saguṇa Brahman with form is the step towards realization of Parabrahman 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.