We have all seen it, Black, brown, yellow even white nasty stuff growing in our bathrooms, on clothing in our closet, even on the outside of our house and roof. It even infiltrates areas we cannot see like like air ducts, remote attic or basement spaces, or wall cavities.
Where does it come from and how do we rid ourself of it.

Algae is a primitive organism that contains chlorophyll and carry on photosynthesis but lacks true roots. There are approximately 25,000 known species of algae in existence. Although algae are not fungus, they closely resemble fungi in appearance. Because algae contain chlorophyll, they are able to manufacture their own food. Therefore, they are the most difficult to eliminate. Algae grow and multiply in moist environments.

Fungi are the broad classification of spore producing organisms usually classified as plants that lack chlorophyll. Fungi include molds, mildews, rusts, smuts, mushrooms and yeasts. There are approximately 50,000 known species of fungi in existence. Fungi live in many types of environments. They thrive in moist, tropical climates. Fungi do not contain chlorophyll and, therefore, cannot manufacture their own food. Fungi maintain their existence by absorbing the minerals, sugars and water from the host on which they live. Fungi use spores as a reproductive mechanism. The wind scatters the spores which then establish and develop into new fungi.

Mildew is the name for certain organisms and the plant diseases they cause, and the discoloration and disintegration of materials caused by fungi. It does not contain chlorophyll and, therefore, cannot manufacture its own food. Its growth is encouraged by high humidity and limited air circulation. It frequently attacks exterior painted surfaces which provide a food source. Mildew forms as tiny dark spots (usually brown, purple or black) which result in an unattractive, dirty appearance

Molds are a member of the fungi family. Molds do not contain chlorophyll and, therefore, cannot produce their own food. Molds can live off of a tremendous variety of food sources as well as reproduce in large quantities.
Mold spores travel through the indoor and outdoor air continually. When mold spores land on a damp spot indoors, they may begin growing and digesting whatever they are growing on in order to survive. There are molds that can grow on wood, paper, carpet, and foods.  When excessive moisture or water accumulates indoors, mold growth will often occur, particularly if the moisture problem remains undiscovered or un-addressed.

How to  Clean Mildewed Surfaces.