Final answer:
A rock with high porosity but low permeability can store a lot of fluid but restricts fluid flow, making it act like a container that holds but doesn't easily release fluids.
Step-by-step explanation:
If we say that a rock has high porosity but low permeability, we mean that the rock has a significant amount of space between its grains that can be filled with fluids like water or oil, but the connections between these spaces are poor, restricting fluid movement through the rock. For instance, a rock might be like a storage room filled with loosely packed basketballs; it can hold much water (high porosity), but if the basketballs are not touching one another, the water cannot easily move from one space to another (low permeability).
Materials with such characteristics might be suitable for containing fluids because they can store them but don't let them flow freely. This is important in nature and industry, as in the case of caprock formations that trap oil or gas underneath, preventing them from escaping due to their low permeability.