The key distinction between a concave mirror and a convex mirror lies in the curvature of their reflecting surfaces. A concave mirror has an inward-curved surface, resembling the interior of a sphere. This concave curvature enables the mirror to converge light rays, allowing it to form both real and virtual images. In contrast, a convex mirror has an outward-curved surface, resembling the exterior of a sphere. This convex curvature causes the mirror to diverge light, resulting in virtual, upright, and diminished images. The direction of curvature determines whether a mirror is concave or convex, influencing its reflective characteristics.