Which statement best describes porosity?

Porosity refers specifically to the amount of open space or voids within a rock material. These voids can be filled with air, water, or other fluids, and they are critical in determining how much fluid can be stored within the rock. This property is essential in fields such as geology, hydrogeology, and petroleum engineering, where understanding how fluids move and are stored in subsurface environments is crucial. High porosity indicates a greater ability to hold fluids, while low porosity means less capacity for fluid retention. Therefore, the choice accurately captures the essence of what porosity measures in geological contexts.