Mold is a type of fungus that grows throughout the environment in a moist environment that contains organic matter. Molds play an important role in nature by breaking down dead organic matter. However, molds growing indoors can cause health problems for people. Molds can produce allergen and irritants that may cause allergic reactions in sensitive individuals. You can control mold growth in your home by controlling the moisture in your home.
MN Dept. of Health - Printable Fact Sheet
EPA - Mold Resources
Printable home mold guide-EPA