What is the significance of Puja (or prayers) done at the temple?
Hindus think of the temple or mandir as the home of God on earth. People go to the temple so that they can see the image of God. This is called darshan. An offering of flowers or fruits may be taken to the temple. Shoes are left at the entrance to keep the temple clean. A bell at the entrance may be rung to announce one's presence. Devotees bow to the image of God at the centre of the temple, and to other deities placed on the surrounding walls. People are seen walking around the central deity, always keeping the deity on the right hand side. The congregation takes part in the arati ceremony. When the arati hymns are sung, everyone joins in. The singing is sometimes accompanied by musical instruments At the end of the ceremony, the arati tray is passed around, and people cup their hands over the arati flame to receive God's blessings. At the time of leaving, everyone gets some prasad to eat.
Going to the temple, is like visiting the home of our real father and mother, who is God. The sight of the majestic temple reminds us about the majesty of God. The centre of the temple is called garbha-griha. The image of the main deity is kept here. When the devotees catch sight of the image they feel satisfied, they feel that they have actually seen God. When so many devotees meet up at the temple either for the worship ceremony or to celebrate festivals, they feel nice because they feel they belong to a larger family.
Reference: Primary Hinduism by Seeta Lakhani (Ch.5, 'Worship And Celebration', p.57)