Mold and mildew share somethings but are different in ways too. They are both types of fungus. Mold can penetrate a service and mildew remains on the surface. How can you tell the difference? Mildew is usually flat and is usually white/gray/or yellow in color, but will turn black/brown over time. Mildew is also usually found on or around a wet or moist surface. Mold is usually fuzzy and will show up in different shaped spots. Mold can have many different colors.
Not sure how to tell if something in your home is mold or mildew? One way to find out is to drop a couple drops of bleach on the surface and if it starts to lighten up then its mildew. If the area stays dark, it is most likely mold. You can also buy testing kits or hire a professional if you aren’t sure what it is. Now that you know what it is, how do you clean it? If it is mildew, you can use cleaners and a scrubbing brush to get rid of it. If it is mold, you will want to contact a professional, so you are sure that it is all removed.
The best thing to do is contact a professional to determine what it is and how to remove it.