Final answer:
Groundwater exists beneath Earth's surface as a liquid, occupying the pore spaces between particles or within fissures in rocks, and it is a critical source of fresh water for drinking and irrigation.
Step-by-step explanation:
Groundwater exists beneath Earth's surface primarily as a liquid. It is found in the spaces, known as pore spaces, between particles of dirt, sand, and gravel, or within the fissures in rocks. Groundwater flows through these spaces and eventually contributes to the surface water found in streams and lakes. It is crucial to note that while water can exist in different states, such as liquid, gas, or solid, and substances like metals can dissolve in other solids to form solid solutions, groundwater itself is largely present as liquid water in the subsurface layers of the Earth. This liquid water moves from areas of higher elevation to lower elevation and is a vital source of drinking and irrigation water, which is accessed through wells.