What is meaning of Vertical Shear and Longitudinal Bending in still water on ships?

A ship floating in still water has an unevenly distributed weight owing to both cargo distribution and structural distribution.

The buoyancy distribution is also non-uniform since the underwater sectional area is not constant along the length. Total weight and total buoyancy are of course balanced, but at each section there will be a resultant force or load, either an excess of buoyancy or excess of load. Since the vessel remains intact there are vertical upward and downward forces tending to distort the vessel ,which are referred to as vertical shearing forces, since they tend to shear the vertical material in the hull.