Rain are water droplets. These are formed by clouds. They appear as water shower. Phenomena of rain is actually a water circle.

During summer, the heat from the plants, trees and water gets converted from moisture into water vapor. This vapor disappears in the air.

These vapors when reach a height, form tiny water droplets that convert into clouds.

When the weight of these clouds increase due to increase in the number of water droplets combining together, it causes rain shower.

Hence causes the rainy/monsoon season.

However, rain is major part of precipitation.

I hope this answer helps!😊