What is meant by vertical shift and lateral shift. Find the difference between vertical shift and lateral shift

Dear student When a ray of light travels through a glass slab from air, it bends towards the normal and when it comes out of the other side of the glass slab, it bends away from the normal. It is found that the incident ray and the emergent ray are not along the same straight line, but the emergent ray seems to be displaced with respect to the incident ray. This shift in the emergent ray with respect to the incident ray is called lateral shift  When the object and the observer are in two different media,the image of the object appears like shifted from original position and it is called vertical shift Regards