Reflection of light
We can see a light bulb because it emits light which enters out eyes and is detected there. We can see a dog, not because a dog emits light but because light from a source, such as the Sun, is reflected from the dog into our eyes.
So if the dog is somewhere there is no light source, such as in a completely darkened room, we will not see it and will probably trip over said dog!
Everything that we see that is not itself a light source is only seen because light from a source has been reflected from its surface.
The light from an uneven surface, such as a dog or a desk, is reflected from the surface in all directions - this is called scattering.
Light sources can be weak or strong, e.g. a small torch or a bright spotlight. The intensity of light also falls off with distance from the source. Hence staring at a spotlight which is close to the eye could cause damage but the further someone is from the same spotlight, the less bright it will seem. Many of the dim starts in the night sky are actually much brighter than our Sun but are very, very far away.
ContentsSight, Safety, Light needs a source, Speed of Light