The rays are real. When I see a pen in the day time with my eye, it means the light rays from the Sun are reflected by each point on the pen, and they reach my eye. My eye focuses them on to the retina. I get the sensation.
When multiple rays coming out of a point on an object, fall on the mirror at different parts of the mirror and they get reflected. For a concave mirror, they all intersect at one point. That point is the image. This is the mathematical way of finding image and this is what happens.
Rays from a convex mirror do not meet at one point. So they do not form a real image. But the rays appear to diverge from one point behind the mirror. Our eye does the intelligent work of imagining that the object is present behind the mirror.
