Molds are eukaryotic organisms. This means that their cells have nuclei and mitochondria. Molds and yeast are fungi.
Molds require a preformed source of organic carbon.
For this reason, they are omnipresent in the environment. This means they grow everywhere and on everything. Generally, they like warm, moist environments. Furthermore, they can grow under more strenuous environments than bacteria, and are responsible for the spiolage of certain foods like jam, cheese and bread. Bread you buy from the store has some preservatives in it which help prevent the growth of mold and bacteria.