https://en.wikipedia.org/wiki/Porous_medium
A porous medium or a porous material is a material containing pores (voids). The skeletal portion of the material is often called the "matrix" or "frame"
Material porosity and permeability
A porous material most often refers to porous solids, i.e. porous materials where the matrix is a solid.
If the porosity of a porous solid is high enough, it is also falls under the category of Foams, and many of these are very flexible materials.
Solid-gas Dispersed media do form materials with pores, but they are different from porous solids in that the location of these pores can change as the material is strained or disturbed in some way.