When we talk about reflections we most often think about a reflection in a mirror or other shiny surface. In science a reflection is what happens when any sort of wave is caused to change direction by something ... but the change in direction is less than 180^o.

In other words; light, sound, and radio waves can all be reflected by different objects. The angle at which the wave hits the object is called the angle of incidence and the angle at which the wave bounces off is called the angle of reflection.

In a reflection, the angle of incidence is the same as the angle of reflection.

So, if the waves hit the reflecting surface at a low angle they will bounce off at a low angle and if the waves travel straight down towards the mirror they will bounce straight back up again at the same angle.

Sound travels from one place to another in the form of a longitudinal wave. Because it is a wave, sound can be reflected when it hits certain objects.
We often call a reflected sound wave an echo.

Echoes are used by bats to find insects in the night. Because it is night-time there is no light to see the insects so the bat produces millions of clicks which reflect off the insect and travel back to the bat ... the bat can then work out where the insect is. This is called echo-location.

Humans also use sound to hunt animals: trawlers fishing in deep water can locate large shoals of fish by producing sounds which travel down through the water; are reflected off the fish; and then bounce back up to the boat. This is called sonar.