Porosity refers to the measure of empty spaces, or pores, within a material. It indicates how much fluid, such as water or air, can be stored in that material. Porosity is commonly found in natural substances like soil, rock, and even some types of concrete. The higher the porosity, the more fluid the material can hold. In geology, porosity plays a crucial role in the movement of groundwater and the storage of natural resources like oil and gas. Different materials have varying levels of porosity, affecting their ability to absorb and transmit fluids. Understanding porosity is essential for fields such as hydrology and petroleum engineering.