A shack is a small, simply-built house. Shacks are often seen near the beach or in the wilderness.
Another word for shack is hut.
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.
Something is shaggy if it is covered in long, thick, scruffy, untidy hair.
You shake something when you move it vigorously up and down or from side to side. The dog in the photo is shaking water out of its coat. People shake drinks like milk to make them frothy.
Shaking can be used to communciate too. People shake their heads from side to side to mean "no", and two people will shake hands as a greeting.
