The full name of the painting is "Woman with a Parasol - Madame Monet and Her Son", painted by Claude Monet in 1875, and now in the collection of the National Gallery of Art, Washington, DC (where I saw it). The subject is Monet's first wife, Camille (model, inspiration, she deserves a story of her own), and their son Jean.
The theme could be the great bond between a mother and her child, because the primary focus is on the mother, standing in the centre of the painting, but the eye is somehow drawn to her son, slightly hidden on the hill behind her, watching her.
However, the colour and movement of summer are probably the true themes of the painting, with the warm soft colours of summer, as the mother stands on a pleasant hill-top, with her skirt billowing in the wind, and Monet is showing how impressionism can convey this better than any other style of painting.
