Paper pads and paper blocks may look similar, but they are bound in different ways. This affects how the paper is removed and how it behaves when you work on it.
Gummed Pads
Gummed paper pads are glued along one edge only, usually at the top, and the remaining three edges of the paper are loose.
This allows you to tear or peel each sheet away easily before or once you have finished working.
They are sometimes called glued pads or just paper pads.
Paper Blocks
Paper blocks are glued on all four edges, so that sheets have to be sliced free using a palette knife or similar tool.
The glued edges hold the paper taut while you work, helping to reduce buckling when using wet media such as watercolour.