Final answer:
Aquifers in porous media consist of rocks that are permeable and have high porosity, allowing for the flow of significant amounts of water.
Step-by-step explanation:
Aquifers in porous media or materials refer to geologic units that have the ability to yield significant water. They are made up of rocks that are permeable, meaning they have the ability to transport fluids. Good aquifers are typically sedimentary rocks such as sandstone and limestone, which have high porosity and interconnected open spaces that allow water to flow through. On the other hand, impermeable rocks like shale or un-fractured igneous or metamorphic rock act as confining layers and prevent the flow of water.