A concave mirror is a curved mirror that bulges inward, resembling a portion of a sphere. It reflects light inward to a focal point, making it useful in various applications like telescopes and shaving mirrors. When an object is placed in front of a concave mirror, it can produce real or virtual images depending on the object's distance from the mirror. These mirrors are commonly used in optical devices and lighting systems because they can concentrate light and enhance visibility. The focal point is crucial for understanding how concave mirrors work, as it determines where the reflected light converges.