Black mold is a fungus or yeast that grows in wet areas of the home like showers or walls. The mold will release spores into the air. If these spores reach your lungs, they will produce asthma- and chronic fatigue-like symptoms.
To remove the mold, spray liquid silver sol on it and let it stand for 10 minutes before wiping it off. This will destroy the mold and likely prevent it from re-growing.