In astronomy, an eclipse is where various planetary bodies align and block the light from the sun. In a lunar eclipse, the Earth comes between the sun and the moon. In a solar eclipse, the moon comes between the Earth and the sun. The picture is of a solar eclipse.
In general language, you eclipse someone if you do something so much better or more obviously than they do that everyone notices you and not them, for example "her beauty eclipsed all others at the dance".
When you stand in front of a light like the sun, some of the light hits you and some of the light goes past you. Where you are in the way between the sun and the ground, there will be a shadow. A shadow is just somewhere there is less light than there is around it. Shadows are the same shape as whatever is blocking the light.
Shadows change size and shape depending on how high or low the light is. Shadows are darker and clearer when the light is strong and coming from only one direction. You can make shadow puppets with your hands or some cut-out shapes, a light and a wall.
When you go out in the sun, you can get sunburnt. Pale skin is more likely to burn than dark skin. Your skin tries to protect itself from the sun by producing melanin, which makes your skin darker. We call this a suntan. The people in the picture have darker skin where the sun has been shining on their skin, and paler skin where it was protected by their shoes.