* Porosity: This refers to the amount of empty space within a rock. It's essentially the percentage of the rock's volume that isn't made up of solid material. A rock can have lots of empty spaces, even if those spaces are very small and isolated.

* Permeability: This refers to how easily fluids (like water or oil) can flow through the rock. It depends on the size and interconnectedness of the pores. Even if a rock has high porosity, if the pores are small, disconnected, or irregularly shaped, fluids will have a hard time moving through.

Example: Imagine a sponge. It has a lot of empty space (high porosity) but the spaces are small and interconnected. Water can easily flow through it, meaning it has high permeability.

Now imagine a piece of granite. It might have many tiny air pockets (high porosity), but these pockets are isolated and don't connect to each other. Water would have a hard time flowing through it (low permeability).

In summary:

* A rock can have high porosity (lots of empty space) but low permeability (difficult for fluids to flow). This is because the pores might be too small, disconnected, or irregularly shaped for fluids to pass through easily.