Ramayanam is a story of Lord Rama, who was the eldest son of Dasaratha, the King of Ayodhya. Ram has three younger brothers namely Lakshmanan, Baratha, Chatrughnan. After the King Dasaratha, It was Ram who should have been the King of Ayodhya. But Barathan's mother and Ram's step mother, Kaikeyi, wanted her son Barathan to be the next king. Her mind was deeply poisoned by Manthara.
King Dasaratha had promised Kaikayi during their Marriage to grant her two boons, she ordered Dasaratha that Lord Ram should be sent to the forest for the next fourteen years and Barathan should be crowned as a next king. Dasaratha kept his word and asked his son Ram to leave for the forest with a broken heart.
Lord Ram accepts the exile and leaves the kingdom, accompanied by his wife Sita and younger brother Lakshmanan. When Barathan came to know about this exile made by his mother, he requests Lord Ram to return back. But Ram refused to do so, hence Barathan took Ram's slippers and places them on the throne as a gesture that Lord Ram is truly ruling the country.
Later Ravana, the evil Srilankan King abducts Sita. How Ram, Lakshmanan and Hanuman fights with Ravana and get Sita back is the rest of the story.