The water cycle is how water moves around the Earth. The Sun heats up water and it evaporates into the air as water vapor. The water vapor then cools down and turns back into liquid droplets, forming clouds. When the droplets get too heavy, they fall back to the ground as rain, snow, or other forms of precipitation. This water collects in rivers, lakes, and oceans and starts the cycle again. It's like a big recycling system for water on our planet.