Golf balls have dimples for the same reason. We've all been annoyed by the person in the Lygon Street restaurant speaking unreasonably loudly into their mobile phone. It may come as a surprise that the person on the other end of the conversation, perhaps down in Geelong, will hear what the caller is saying before you do, even though you are sitting only a few metres away. A consequence of this speed is that it takes light about eight minutes to travel from the sun to Earth. They don't behave like regular flat mirrors because they always reflect the light that strikes them back to where it originated.
Light bounces off a flat mirror just as a ball bounces off a flat surface.
What strikes at an angle bounces off at an angle. A corner reflector is three flat mirrors each set at right angles to the other two. When a beam of light strikes the reflector, it bounces off each of the three mirrors and returns to its source. Hitting a squash ball hard and low down into one of the back corners of the court will produce the same result. The ball will bounce straight back at you.