Simplify the following text for a Grade 6 native English-speaking person.
Original: A stratus cloud ( St ) is a cloud belonging to a class characterized by horizontal layering with a uniform base , as opposed to convective clouds that are as tall or taller than wide ( these are termed cumulus clouds ) . More specifically , the term stratus is used to describe flat , hazy , featureless clouds of low altitude varying in color from dark gray to nearly white .
Simplified: Stratus clouds are low altitude gray clouds that make a flat base .