Reflection

If you look in a mirror, you see your own image. You (the object) and your image appear to be the same distance from the mirror.

An object and its image are always the same perpendicular distance from the mirror line. (Perpendicular means 'at right-angles to'.)

Look at the following examples:

Reflecting a shape diagramReflecting a shape diagram

Each point and its image are the same distance from the mirror line.