I saw this painting last week in Florence. It's displayed in Palazzo Pitti, in the Galeria Palatina. Rafaello painted this around 1513-1514, and it is famous because it's so different in style from the more typical Madonna-paintings he made. The virgin is seated in a chair, thus the name of the painting, and she is dressed like a contemporain country girl. She holds baby Jesus, while John the Baptist is humbly watching her, while showing his devotion.