The document describes four main types of clouds: cumulus clouds which are white and puffy indicating fair weather but can turn into cumulonimbus clouds; stratus clouds which are low and flat gray layers that appear as fog when close to the ground; cirrus clouds which are thin and white consisting of ice; and cumulonimbus clouds also known as thunderheads which are large, puffy and dark storm clouds. The document also notes that cloud names come from Latin roots referring to their characteristics and provides examples.