Who is Robert Baratheon from A Clash of Kings and what is their importance?

Robert Baratheon is the deceased king of the Seven Kingdoms. He was married to Cersei Lannister, and the realm inaccurately assumes him to be the father of Joffrey, Tommen, and Myrcella Baratheon. Cersei's brother Jaime, however, is their true father. Robert was killed after Cersei and Ser Lancel Lannister conspired to give him more potent wine before a hunting trip, which resulted in his death when a boar attacked him.