Seventh incarnation of Lord Vishnu and the the second (after Lord Sri krishna) most popular amongst the dasavatar of Lord Vishnu.
Legend is that Lord Vishnu took human form as son of King Dasaratha and Kausalya to kill Ravan- the demon king of Sri Lanka.
Ramayan- the Hindu epic of Sage Valmiki describes the story of Lord Sriram beautifully. According to it, Lord Sriram had a vanavas to fulfill the wish of his father, along with Devi Sita- his wife. During that time the demon king Ravan kidnapped Devi Sita to Lanka.
Lord Sriram, with help of the monkey force of Sugreev and Hanuman, defeated his force and killed Ravan .There after they returned to Ayodhya and Lord Sriram became the ruler of that land. This is the gist of the epic Ramayan.
More than a story or a religious book, Ramayan influenced the life of an Indian in many ways. It has marked its presence in all walks of life- be it family life, art, literature, music, architecture and what not.
For a devote Hindu, Lord Sriram is the epitome of righteousness and a role model ruler.
There are many temples dedicated to him all over the Indian sub-continent. Here is a list of more famous among them.