Some use the term of mold and mildew as interchangeable  words but below is a more nuanced look at each.  Mildew is wet mold it is slim like.  It is most found in wet areas like showers of sink basins.  This mold is mostly 2 dimensional as it is flat.  It can be most colors, not just black.  when its on hard surfaces it is easy to scrub and remove. Mold has a hypha structure similar to a tree.  It has finger branches on top the cilia ( which can give mold a fuzzy appearance) the middle is has a stem structure and the bottom has a root systems.  The moisture amounts on surfaces that breds mold typically have less moisture content in it than mildew.  Mold can be all colors and not just black. When found on soft surfaces Mold needs to be removed with the materials it is growing on and disposed. ​So which is more dangerous.  Both mold and mildew have the same types it’s all a mater of what state you find them in wet or more dry.