The groundwater cycle (aka water cycle) is the process in which water is cycled from the sky to the ground and back.
First, it moisture in the atmosphere condenses and falls in the form of precipitation (snow, rain, hail). Once it reaches a surface, it is either absorbed by the ground or runs off. This is where the road splits briefly.
Ultimately, the runoff will reach a large body of water and the absorbed water infiltrates the groundwater. The runoff water, now grouped into a larger body, will start to evaporate and reach the atmosphere, completing its cycle. The groundwater on the other hand has one more step; after it reaches the groundwater, plants and trees will use it in the process of photosynthesis. After this, transpiration occurs, and the water in the plant's roots reaches leaves, where it turns to vapor, and goes back into the atmosphere, completing the cycle.
This cycle constantly goes on, and is why there is so much water and precipitation on Earth. For further reference, check the illustration below!
