The Water Cycle (also known as the hydrologic cycle) is the journey water takes as it circulates from the land to the sky and back again. Water can change states among liquid, vapor, and solid at various places in the water cycle.
The Sun's heat provides energy to evaporate water from the Earth's surface (oceans, lakes, etc.) The water vapor eventually condenses, forming tiny droplets in clouds. When the clouds meet cool air over land, precipitation (rain, snow) is triggered, and water returns to the land (or sea). Some of the precipitation soaks into the ground. Some of the underground water is trapped between rock or clay layers; this is called groundwater. But most of the water (above ground or underground) eventually returns to the Oceans.