Cumulus  

Pc: Co Clouds 

These clouds are the clouds that we learn how to draw in our early days . They are very fluffy and very round with odd shapes.

Stratus 

Pc: Wikimedia  Commons

Stratus look very dull and they cover the whole sky with layers for clouds. They seem like fog but in the sky.

Altocumulus 

Pc: Flickr

These clouds are in gray and white and they make patches that cover the middle of the atmosphere.

Cirrostratus 

Pc: Wikimedia Commons

The clouds seem to be there but not at the same time. That is because the clouds are transparent.