What is the main characteristic of porosity?

The main characteristic of porosity is that it can be used as a measure to determine the degree of voids present in the rocks.

Explanation:

The more porous the rock is, the more voids it has. This relation between the porosity and the degree of voids in a rock makes porosity a good parameter of measuring the extent of voids in the rocks. Moreover, porosity also enumerates the ability of a material to absorb and hold fluid. This is particularly because the pores act like openings for the fluids coming in and falling out of the material.