Rain is a type of precipitation, as is snow, sleet, hail, dew or fog. Precipitation is where water vapour in the air is cooled and condenses into water droplets giving rise to different forms. We need to know how much rain or snow falls on average in a place and also how likely it is for it to occur.
Water is fundamental to all forms of life and farmers depend on the weather providing them with enough rain and other moisture to keep their crops growing and their animals alive. Drought is a huge problem in some parts of the world. But even where it rains on and off all year, we need to know how much and when so that we can make sure we build houses that will not leak, take an umbrella or a coat if we have to go out somewhere, or guess if we will have to cancel the football match.