Water flows underground between cracks in rocks or pore spaces in soil.
Groundwater fills wells and flows through water bodies like lakes, reservoirs, and the ocean. When we dig a well, where we first hit water is the water table , or the top of the groundwater. The level of the water table varies. It is not flat as its name suggests, but somewhat mimics the topography of the land. If a lot of water is withdrawn from the groundwater supply for consumption, the level of the water table goes down.