Cumulus clouds are puffy, white clouds that generally form in fair weather and are often seen as small, isolated clouds. They form when warm air rises due to convection.Nimbus is a term used to describe clouds that bring precipitation. So, it's not a specific type of cloud by itself but rather a descriptor for clouds that are capable of producing rain or snow.A Cumulonimbus cloud forms when a Cumulus cloud grows significantly larger and vertically due to strong updrafts of warm air. These clouds reach very high altitudes and can extend into the stratosphere. They are the towering clouds often associated with thunderstorms, heavy rain, hail, and sometimes even tornadoes. The "Nimbus" part in the name indicates their capability to produce precipitation, so a Cumulonimbus cloud is essentially a large, storm-producing version of a Cumulus cloud.So, in short, Cumulonimbus clouds are an evolved form of Cumulus clouds with strong upward motion, and they are capable of producing precipitation (hence the Nimbus association).