All the water in the atmosphere is held by clouds. After a while the clouds get heavy and gravity pulls it down in the form of precipitation or rain. When it reaches the ground gravity is still working to bring it to the lowest point. This processes is known as run off.
The water from the run off gets soaked into the soil and plants then use the ground water to help make energy and proteins that it needs to grow.
The water is then taken in by the roots and lifted up the stem to the leaves where it leaves the plant through a process called evapotranspiration.
Run offs also deposit in the ocean. This is where most of the water in our atmosphere comes from. The water from the ocean changes into a gas in a process known as evaporation.
At the end of the water cycle water that was sublimated, evaporated, or went through evapotranspiration, turns into condensation and the cycle starts all over again.