Answer:
As you may already know, water drops that fall from the cloud are considered "rain".
The Sun's heat turns the moisture or water from leaves, plants, rivers, lakes, and oceans - and turns it into gas or also called, vapor. This water vapor then turns into gas and disappears into the air. When it gets mixed with the air, it cools down. When it cools down, it changes into small water drops, which then form a cloud. These small water drops join together with other water drops to create larger and bigger water drops.
You may know this now because this is the easiest part. What happens when something gets heavy or is over-filled? It falls down, right?
So, the large drops from water fall down as they get too heavy for the cloud to carry. These big droplets falling down on us are called Rain.