A convex mirror, or diverging mirror, is a curved mirror in which the reflective surface bulges toward the light source. Such mirrors always form a virtual image, since the focus F and the centre of curvature 2F are both imaginary points "inside" the mirror, which cannot be reached.

A collimated (parallel) beam of light diverges (spreads out) after reflection from a convex mirror, since the normal to the surface differs with each spot on the mirror.

A concave mirror, or converging mirror, has a reflecting surface that bulges inward (away from the incident light). Unlike convex mirrors, concave mirrors show different types of image depending on the distance between the object and the mirror itself.

These mirrors are called "converging" because they tend to collect light that falls on them, refocusing parallel incoming rays toward a focus. This is because the light is reflected at different angles, since the normal to the surface differs with each spot on the mirror.