Rock Porosity
Rock porosity is the amount of tiny open spaces inside a rock that can hold water.
Think of it this way
A dry sponge has many small holes inside it. Water fills those holes when you dip the sponge in a bowl. A rock works the same way — its tiny gaps hold water or air. A rock with more holes stores more water than a solid block.
Explaining rock porosity by grade level
Some rocks have many small holes inside them, like a sponge. When you pour water on a rock, those holes soak it up and hold it. Rocks with more holes hold more water. Rocks with fewer holes let the water run off.