Scientifically defined, reflections are the changes in the direction of waves, which occur as a wave strikes an object and then travels back through the medium it came from. When we speak of reflections, it most often refers to light waves or visual images. All types of waves can be reflected, including waves in water, as well as light and sound waves. The behavior of particular reflections depends on the type of energy being carried in the wave.
One example of this is the contrast between reflections of light and those of sound. An echo is a sound wave that is reflected, but it is not always easy to tell the origin of the sound wave. Light waves, though, follow a completely different and stricter set of rules. Light waves follow what is known as the law of reflection, which states that the angle at which light strikes a smooth reflective object is equal to the angle at which it is reflected.
The law of reflection does not mean that light always bounces back from where it came. Instead, if the light strikes at a steep angle, for example, it will be reflected at the same steep angle, but in the opposite direction. We can observe this from the angle at which the image of a cloud or a mountain is reflected in a calm lake, or in the way a mirror at the correct angle can allow us to see around a corner.
Even objects which are not smooth reflect light, although in a different way. These kinds of reflections are what constitute an object's color. For example, the red petals of a rose are red because they reflect the red wavelengths of visible light. Other wavelengths are absorbed, but the ones that are reflected scatter in all directions, and reach our eyes in this way. The same principle applies for any object we observe, namely that we see it only because it reflects light toward our eyes.
Some materials exhibit a property known as total internal reflection. This means that light waves traveling through such a medium are stopped from exiting it, and are reflected back into the medium at the same angle. Fiber optic cables have this property, allowing them to carry light waves in circles, around corners and over long distances. The light only exits when it reaches the end of the fiber. The surface of water can also cause the same phenomenon, when observed from underneath.