Reflection of light rays or any electromagnetic waves:
When electromagnetic waves are incident on a boundary of two media, part of it is bounced back or turned back in to the first medium. This is called reflection. The reflected rays or waves follow the rule that angle of incidence is same as angle of reflection at the point of incidence.
When light rays are incident on a boundary between two different transparent media, then light bends at the boundary and enters the second medium. The angle of incidence and angle of refraction in the second medium are different. If the second substance is more dense than the first, then light bends towards the normal drawn at the point of incidence.