Rama Navami celebrates the birth of Lord Rama, an incarnation of Lord Vishnu and a just-ruler whose reign is a symbol of peace and prosperity. It is also significant as it is celebrated in the beginning of summer when the Sun is moving towards the Northern Hemisphere and Rama is supposed to belong to the Sun dynasty. The birth and story of Lord Rama is chronicled by Sage Valmiki in the epic Ramayana, meaning Rama’s journey.
Lord Rama is believed to be born on the ninth day of the bright fortnight (Sukla Paksha) in the month of Chaita, the first month of the Hindu Calendar. As He was born mid-day, people usually fast till mid-day, in anticipation of the Lord’s birth and then break the fast with the offerings to God. In South India, we usually make panagam (water sweetened with jaggery and spices), neer mor (watered down butter milk) and kosumbari (pre-soaked moong dhal flavored with green chillies and ginger) as offerings on Rama Navami.
The virtues of Lord Rama and why His worship is important is beautifully explained here.