This can be compared to water in a sponge. If water is pored onto a sponge it will slowly saturate the entire sponge. This layer extends downward until it reaches a layer of impervious material that the water cannot penetrate. The top of the zone of saturation is known as the water table. The ground materials above this point are not saturated.
Ground water behaves much like surface water in that it flows from high areas to lower areas.
As it reaches these lowland areas, it often escapes to become surface water. This can occur in several ways. Natural springs can exist in which the ground water simply breaks through to the surface. It can also leak into streams and rivers. Many streams would become completely dry during periods of drought if it weren't for being constantly fed by the ground water which isn't as easily affected by surface weather conditions.