The src attribute provides the location of the image. The srcset attribute provides the locations of alternate versions of the image for different display resolutions.
The sizes attribute provides different image sizes based on the viewport width.
Art direction involves changing the image itself for display on different size screens. This might mean providing the full image for a desktop display and a cropped version for smaller displays.
The src attribute provides the loction in which the image can be found. The srcset attribute provides different versions of the image for display on different screen resolutions. The sizes attribute provides different image sizes based on screen size. Art direction involves changing what parts of the image are displayed to fit different displays.