Why do you see a shadow?

You see a shadow because your hand blocks the light from reaching the wall behind it. Light travels in straight lines and can't bend around solid objects, so wherever your hand sits between the flashlight and the wall, no light gets through to that spot, leaving a dark shape shaped just like your hand.

Light doesn't bounce backward to make a shadow — that's closer to how a mirror or reflection works, not a shadow. And the wall definitely isn't glowing; it's actually the opposite, the shadow area is where light is missing, not where extra light is appearing.

Your shadow stretches longest in the early morning and evening because the sun sits low near the horizon then, sending light in at a shallow slanted angle, while at midday, when the sun is high overhead, your shadow shrinks to its shortest.