There are lots of light sources: sun, bulb, torch, candle.
Transparent objects allow all light to pass through.
Translucent objects allow some light to pass through.
Opaque objects don't allow any light to pass through.
There are many things that reflect light such as: mirrors, eyes, foil, spoons.
I did an experiment with a torch.
Shadows are formed by blocking light. If an opaque object gets in the way, it stops the light rays from passing through. This makes an area of darkness (a shadow).
I used lego to make a shadow.