What are puffy white clouds often flat what are the called?

Puffy white clouds that often appear flat on the bottom are called cumulus clouds. These clouds form when warm, moist air rises and cools, causing water vapor to condense into visible droplets. The flat base is a result of the condensation level, where the temperature and pressure cause the air to reach saturation. Cumulus clouds are typically associated with fair weather, although they can develop into larger storm clouds under certain conditions.