Object at center of curvature:- When the object is placed at the center of curvature of a concave mirror, the image formed is also at center of curvature, same in size, real and inverted.
Object beyond center of curvature:- When the object is placed beyond the center of curvature, the image formed is in between the focus and center of curvature, the image is smaller is size than the object (diminished), real and inverted.
Object at infinity:- When the object is placed at the infinity form the concave mirror , the image formed is at the focus, highly diminished, real and inverted