What is the difference between porosity and permeability

Porosity is the percentage of spaces, (hollow) within a rock or a material that can contain air or fluid. This can be used in geology (study of rocks), soil mechanics, engineering and pharmaceutics. Industrial CT scanning can be used to test for porosity of a substance. While permeability is the ability of water or other fluids to flow through a rock or material that has spaces (that is, that are porous). This is also applicable in the fields of chemical engineering and geology.