The document discusses the process of rain formation. It begins with a general statement that rain is a primary source of freshwater that provides suitable conditions for diverse ecosystems. It then explains the water cycle process where the sun heats water on Earth's surface causing evaporation, the water vapor rises and cools in the atmosphere condensing into liquid droplets, and the droplets fall to Earth as precipitation such as rain or snow. However, not all rainfall reaches the surface as some evaporates through dry air in a phenomenon seen in hot, dry desert regions.