The mirror reflection is a type of symmetry called reflection symmetry across the mirror plane.

Reflection symmetry means one half is a mirror image of the other across a line or plane. In the case of a flat mirror, the plane of symmetry is the mirror surface itself. The mirror creates an image where every point is flipped across this plane, which swaps front and back. Left and right, or up and down, are preserved unless you turn your body or the mirror, because the mirror has no way to distinguish left from right or up from down.