Pūjā (alternative transliteration pooja, Sanskrit: reverence or worship, loosely) is a religious ritual which most Hindus perform every morning after bathing and dressing but prior to taking any food or drink. Puja rituals vary between Hindu sects, but generally involve the chanting of a particular mantra on a mala (rosary) and optionally the offering of food and drink to one's personal murtis of god and guru.
A puja can be performed for anyone the performer considers to be his conception of God, from a murti of Vishnu to a Siva linga. The worship consists of offering something to the object of worship, such as flowers or food, and possibly lighting a candle or incense. The puja represents welcoming ceremony and thus is also performed for prominent guests to one's home. In the Vedic tradition a random guest is considered as good as God (atithi Narayana).
The ritual may be observed in silence or accompanied by prayers. A Hindu priest will chant prayers in Sanskrit or some other language while performing puja. One who assists the priest (pujari) in rituals is called tantra-dharaka .
The Hindu Individual or Group Puja consists of meditation (dhyana), austerity (tapa), chanting (mantra), scripture reading (svadhyaya), offering food (thaal) and prostrations (panchanga or ashtanga pranama, dandavat). The individual also applies a tilaka mark on the forehead with sandalwood paste, and then a vermillion ("kumkum") dot (chandlo) in its centre. This signifies submission to the Almighty and also His Omnipresence.
Puja may be performed by an individual worshipper or in gatherings. Sometimes a puja is done for the benefit of certain people, for whom priests or relatives ask blessings.
Large pujas request the presence of fellow believers and pray to the god or goddesses in question. This usually involves a full day ritual where people are present for the actual puja ceremony and have puja prasad (blessed food that should not be thrown out), and they may go home until later when there are songs or other performed in religious or general context, followed by an all-vegetarian dinner.
The term puja is also used to refer to certain ceremonies performed by Buddhists on holy days. http://www.4dham.com/go2/Puja.html