A spring is a place where the water table reaches the surface of the Earth at an uneven point. Many springs are located on the sides of mountains. These springs act as the sources for streams and rivers as groundwater reaches the surface of the Earth and then begins to flow downhill. In other cases, springs feed pools of water that collect in dips in the Earth's surface.
When the water table intersects a valley across a wide area, the result is a body of still water, such as a lake or pond. Water that would be stored underground runs out of the ground and rests on the surface of the Earth instead. Some lakes are also fed by rain and by rivers carrying water from springs that can be far away. When a lake or pond appears in the desert, it is called an oasis.
The biggest bodies of water, oceans, result from the fact that there is more water than landmass on the Earth. The ground forming the continents and islands of the planet cannot hold all the water, so the water table extends out beyond the edge of continents to form oceans. Oceans are also fed by rain, rivers and runoff from coastlines.
It is possible to create man-made meetings between the water table and the Earth's surface by digging a hole deep enough to hit the water table. Creating a hole that extends below the water table creates a well, or a permanent source of water. Removing water from the well does not make it empty because more water seeps in from the surrounding saturated rocks and soil to replenish the well. A well is, in essence, a tiny, deep man-made pond.